Mission Viejo's Linda Jezek extended her unbeaten streak in backstroke competition to 14 tonight by winning the 100-meter event in a meet-record 1:03.12 at the National AAU Long-Course swimming Championships.

Jezek, a junior at Stanford, was pressed hard by Sue Walsh of Zwicker Swim Club of Buffalo, N.Y. Walsh was second in 1:03.28.

Susan O'Brien, 13, of Curl Swim Club in Bethesda, Md.,placed 15th in the backstroke in 1:06.12. She qualified ninth with 1:05.66.

Rowdy Gaines overtook Brian Goodell in the last 30 meters to win the 200-meter freestyle in 1:50.57. Goodell's time was 1:50.8.

Tracy Caulkins won her first event of the meet, taking the 200-meter individual medley in 2:17.44. The Nashville Aquatic Club workhorse led by two meters with 50 meters to go but had to hold off a strong challenge from Ann Tweedy of the Santa Barbara (Calif.) Swim Club, who was second in 2:18.96.

Jenny Rapp, 16, of Starlit Aquatic Club in Fairfax, Va., finished 11th with a 2:21.39 after qualifying 16th in 2:23.05.

An expected battle in the 400-meter freestyle between Kim Linehan of Austin, Tex., the 800-meter winner, and Cynthia Woodhead, the 100-meter champ from Riverside (Calif.) Aquatics, never materialized. Woodhead set a torrid pace from lane one and won the even in 4:10.27. Linehan finished fourth.

Jesse Vassallo successfully defended his 400-meter individual medley title in 4:25.19, more than five seconds off his world mark of 4:20.05.

Starlit Aquatic Club's relay team of Clay Britt (57.44), Kerwin Gober (1:06.64), Phil Perdue (55.9) and Sam Jones (51.68) placed eighth in the 400-meter medley in 3:51.66. Longhorn Aquatics of Austin, Tex., won the event in 3:49.22.