Her time of 4:03.85 in the 400-meter freestyle was a world record.

In 1989, Janet Evans won seven national championships. She took the 500- and 1,000-yard freestyle titles and the 400-yard individual medley at the short-course nationals, the 400- and 800-meter freestyles and the 200- and 400-meter medley events at the long-course nationals. Those performances won her the 1989 Sullivan Award as the country's outstanding amateur athlete of the year as well as the U. S. Olympic Committee's Sportswoman of the Year award.

Janet Evans was the 200-, 400-, and 800-meter freestyle champion in the 1990 long course nationals, but she lost her 400-meter individual medley crown. She also won the 400- and 800-meter freestyle events at the 1991 world championships.

Swimming for Stanford University, Evans won the 500- and 1,650-yard freestyle events at the 1990 and 1991 NCAA championships and she was the 400-yard individual medley titlist in 1990. However, she left school in 1991 because of a new NCAA rule limiting collegiate swimmers to only 20 hours of practice a week. At the 1992 Olympics, Evans claimed two more medals, a gold in the 800-meter freestyle and a silver in the 400-meter.

Janet Evans gave up the individual medley event in 1993 to focus on her freestyle swimming. The move paid off in another string of victories. She won the 400-, 800-, and 1500-meter events at the national spring and summer championships and was also 400- and 800-meter world champion that year.

She repeated her triple victories at both national meets again in 1994, but claimed only one world championship, in the 800-meter. It was the only victory for an American woman at the world meet, which was dominated by the suddenly emerging Chinese. Janet Evans began to show signs of vulnerability in 1995. After winning the usual three freestyle races at the national spring meet, she didn't win anything at the summer nationals, where her best finish was a second in the 400-meter. At her third Olympics in 1996, Evans didn't come close to medaling, and she announced her retirement from competitive swimming shortly afterward.