The purpose of this study was to compare the postoperative success and stability of two different autografts used to reconstruct the anterior cruciate ligament (ACL): doubled semitendinosus/gracilis (DST&G) and bone-patellar tendon-bone (PAT). Ninety-one young (x = 25.4 years), active patients were available for an average follow-up of 36.4 months and included 55 patients in the PAT group and 36 in the DST&G group. No patients had previously undergone ACL reconstruction. Knee stability data were obtained yearly and included scores from the Lysholm questionnaire, Lachman exam, and KT-1000 arthrometer at 30 pounds (KT30) and maximum pull (KTMAX). Both autografts were of comparable size, tension, and isometricity. Two separate factorial multivariate analyses of variance (MANOVA) were used to compare the two series for 3 follow-up years in the categories acute and chronic (A versus C) and meniscectomy and no meniscectomy (M versus NM). Results indicated that in all categories and follow-up years, PAT patients had consistently greater knee stability compared with the DST&G group. Overall MANOVA results showed significantly lower (p < 0.01) Lachman scores in PAT versus DST&G in each of the 3 follow-up years. Significantly lower (p < 0.05) KT30 and KTMAX values were also observed for PAT compared with DST&G in year 1. MANOVA results also showed lower (p < 0.01) Lachman scores in PAT-A versus DST&G-A for 3 follow-up years. Lachman scores in PAT-NM patients were lower (p < 0.01) for postop years 1 and 2 compared with DST&G-NM.(ABSTRACT TRUNCATED AT 250 WORDS)