He has won seven Cy Young Awards -- two more than any other pitcher has received. He throws and bats right-handed, and currently plays for the Houston Astros.

Clemens made his debut with the Boston Red Sox, where he played for 13 seasons, after which he was famously pronounced to be in "the twilight of his career" and signed with the Toronto Blue Jays. In two seasons with the Blue Jays, he made a comeback as he won the pitching triple crown and the Cy Young award each year. He was traded to the New York Yankees for the 1999 season, where he would have his first World Series success. He won his 300th game in 2003, a rare accomplishment for modern pitchers, and is one of just four pitchers to surpass 4,000 strikeouts. After retiring from the Yankees, he changed his mind and returned in 2004 with the Houston Astros, where he has remained a top tier pitcher.

In 2006, after playing in the World Baseball Classic and not signing with any team through late May, Clemens returned to baseball yet again, signing a 1-year contract with the Astros.

Clemens' parents separated when he was an infant. His mother soon remarried Woody Booher, whom Clemens still considers his father. Booher died when Clemens was nine years old, and Clemens has been quoted from time to time that the only time he ever felt jealous of other players is when he saw them in the clubhouse with their fathers.[2] After living in Dayton, Ohio until 1977, Clemens spent his high school years in Texas. At Spring Woods High School in Houston, Texas, Clemens starred in football, basketball, and baseball.[2] Clemens was drafted out of high school in the 12th round of the 1981 draft by the New York Mets, but did not sign, opting instead to go to college. He began his college career in 1981, pitching for the San Jacinto College North Gators, where he was 9-2 and wore No. 26. His coach was Wayne Graham. He also attended the University of Texas, compiling a 25-7 record in two All-American seasons, and was on the mound when the Longhorns won the 1983 College World Series. He became the first player to have his baseball uniform number retired at the University of Texas.[3]

Clemens was drafted 19th overall by the Boston Red Sox in 1983 and quickly rose through the minor league system, making his major league debut on May 15, 1984. In 1986 his 24 wins helped guide the Sox to the World Series (which they lost) and earned Clemens the American League Most Valuable Player award for the regular season. This was the first of his seven Cy Young Awards (he also won the AL award in 1987, 1991, 1997, 1998 and 2001 and the National League award in 2004).

Hall of Fame slugger Hank Aaron angered the hurler by saying that pitchers should not be eligible for the MVP. "I wish he were still playing," Clemens responded. "I'd probably crack his head open to show him how valuable I was." Clemens remains the only starting pitcher since Vida Blue in 1971 to win a league MVP award.

In 1986, Clemens became the first pitcher in history to strike out 20 batters in a complete 9-inning major league game. (Kerry Wood matched the total in 1998. Randy Johnson also struck out 20 batters in the first nine innings of an extra-inning game, but because Johnson did not finish the start, his performance is catalogued separately by MLB, along with Tom Cheney's 21 strikeouts in 16 innings).

Remarkably, Clemens accomplished the feat twice, striking out 20 Seattle Mariners on April 29, 1986 at Fenway Park, and then doing the same more than ten years later, on September 18, 1996 against the Detroit Tigers at Tiger Stadium. The latter performance occurred in his second-to-last game as a member of the Boston Red Sox.

No Red Sox player has worn #21 since Clemens left the team in 1996.

Notoriously, Red Sox general manager Dan Duquette said Clemens was in the "twilight of his career" and opted not to re-sign him following the 1996 season. However, the full quote from which "twilight" is excerpted was not entirely negative, and also referred to Red Sox management's stated hopes that Clemens would spend his entire career with Boston:

Nevertheless, Clemens signed with the Toronto Blue Jays in the 1996 offseason, and won the Cy Young Award in both his seasons with the Blue Jays, also winning the pitching Triple Crown twice. Some consider Clemens' tenure with the Blue Jays as his best individual seasons of his career, despite the lackluster records the Blue Jays had as a team.

The emphasis on the 1996 "twilight" quote took on a life of its own following Clemens' post-Boston successes, and Duquette was vilified for letting the star pitcher go.[4] As of the start of the 2006 season, Clemens' record since he left Boston is 149-61.

Clemens was traded to the New York Yankees before the 1999 season for David Wells, Homer Bush and Graeme Lloyd. In 1999 and 2000, he won World Series titles with the Yankees.

Clemens' 2000 season was punctuated by a pair of notorious moments involving New York Mets catcher Mike Piazza. During a July 8, 2000 game between the Mets and the Yankees, Clemens hit Piazza squarely in the head with a pitch. Piazza had previously enjoyed great success as a hitter against Clemens (including a grand slam against Clemens one month earlier), which was widely seen as Clemens' motivation. The incident and its aftermath received intense media coverage. Piazza bitterly criticized Clemens, while the Mets were assailed for not "protecting" their star catcher (retaliating by hitting an important Yankee batter). And when both the Yankees and the Mets reached that year's World Series, there was great anticipation regarding the two men's first confrontation since the beaning.

Astoundingly, in that first at-bat (in the 1st inning of Game 2 of the 2000 World Series), Piazza's bat shattered, sending a large piece of the broken bat shard flying in Clemens' direction. Clemens picked it up and threw the broken bat down toward the first base line, missing Piazza but clearing the benches of both teams. Clemens later claimed that he was "fielding" the broken bat, having mistaken it for the baseball. His explanation was widely ridiculed[5], in part because pitchers fielding baseballs hit in fair territory don't typically throw them towards the home plate side of their dugout. Mets pitcher Al Leiter said, "If he felt that way, shouldn't he have thrown it to Tino (Yankee first baseman Tino Martinez)?"

During the subsequent faceoff, both Clemens and Piazza appeared hesitant to confront one another. Dan Shaughnessy of the Boston Globe compared the situation to two schoolyard bullies, afraid to fight, but suddenly forced to. Clemens was not ejected from the game, although he would later be fined $50,000. Following the bizarre incident, he proceeded to shut down the Mets with 8 innings of 2-hit, no-walk, 9-strikeout pitching.

As impressive as this dramatic game was, it wasn't even Clemens' best perfomance that month. In his previous start, in Game 4 of the 2000 ALCS against the Seattle Mariners, Clemens threw a one-hit shutout while striking out 15. Many consider it to be Clemens' best and most "clutch" game as a Yankee. This contest was also marked by gamesmanship, as Clemens knocked down the Mariners' star hitter Alex Rodriguez twice during his first at-bat. (Rodriguez would eventually walk, the only baserunner allowed by Clemens through the game's first six innings.)

In 2001, Roger Clemens became the first pitcher in history to start a season 20-1. He finished at 20-3 and won his sixth Cy Young Award.

On June 15, 2002, Clemens made his first start in Shea Stadium since the two incidents with Mike Piazza in 2000. With Clemens batting against the Mets for the first time, the game represented the Mets' first risk-free chance to "get even" with Clemens for his nearly two-year-old beanball. The speculation was that Clemens was certain to be plunked; the reality was more ambivalent. Mets starter Shawn Estes threw a pitch behind Clemens' back, failing to satisfy the crowd and drawing an umpire's warning (thus preventing Estes from making another HBP attempt). However, the Mets scored four runs off Clemens, including home runs by the two Met principals Estes and Piazza, and handed Clemens the loss.

Early in 2003, he announced his retirement, effective at the end of that season. On June 13, 2003, pitching against the St. Louis Cardinals in Yankee Stadium, Clemens recorded his 300th career win and 4,000th career strikeout, the only player in history to record both milestones in the same game. The 300th win came on his fourth try; the Yankee bullpen had blown his chance of a win in his previous two attempts. He became the 21st pitcher ever to record 300 wins and the third ever to record 4,000 strikeouts, joining Nolan Ryan (5,714) and Steve Carlton (4,136). His career record upon reaching the milestones was 300-155; his record at the end of the season was 310-160 with 4,099 strikeouts.

The end of Clemens' 2003 season became a series of public farewells in which the great righthander was met with appreciative cheering. His last games in each AL park were given extra attention, particularly his final regular season appearance in Fenway Park (a spectacle which was repeated when the Yankees ended up playing the Red Sox in that year's ALCS and Clemens got a second "final start" in his original stadium). Clemens was permitted to manage the Yankees' last game of the regular season. Clemens made one start in the World Series against the Florida Marlins; when he left trailing 3-1 after seven innings, even the Marlins left their dugout to give him a standing ovation.