Seventeen-year-old Steve Lundquist lowered the world record for the 200-meter individual medley to 2:04.39 yesterday during preliminaries on the first day of the AAU National Long-Course Swimming Championships.

Lindquist, who swims for the Tallman Pools Swim Team of Atlanta, broke the mark of 2:05.24 set by the U.S.S.R.'s Aleksandr Sidorenko in January in Moscow.

These AAA Championships are also the U.S. trials for selection of entries in the world championship scheduled for Aug. 18-28 in West Berlin.

Starlit Aquatic Club's Jenny Rapp qualified for the consolation final in the women's 200-meter individual medley, recording 2:21.42 in finishing ninth.

Melissa Belote, formerly of Solotar Swim Team and now swimming for the De Anza Swim Club of Cupertino, Calif., also reached the consolation final with time of 2:21.72.

Tracy Caulkins, the top scorer in the last three AAY championships just missed her pending American record in the individual medley, recording 2:16.01.

Fourteen-year-old sensation Cynthia Woodhead of Riverside, Calif. missed Shirley Babashoff's U.S. record by two-tenths of a second, churning to a 4:10.69 in the 400-meter freestyle.