The purpose of this investigation was to compare the effects of weight training using a single set to failure vs. multiple sets not to failure in young women. The subjects were 17 previously untrained, healthy, college-age women (age 18-20 years; 66.8 Ϯ 12.3 kg). After initial testing, the subjects were randomly assigned to 1 of 2 groups: the single-set group (SS, n ϭ 9) and a multiple-set-variation group (MSV, n ϭ 8). Testing was conducted at the beginning and end of the study. There were no initial differences between the groups. Tests included the 1 repetition maximum parallel squat (1RMS) and countermovement vertical jump (CMVJ). Body mass was measured on a medical scale. Subjects trained 3 days per week for 8 weeks; all training sessions were monitored by investigators. After warm-up, the SS performed 1 set of 8-12 repetitions to muscular failure. If 12 or more repetitions could be performed, an additional 2.5-5.0 kg were added for the next training session. The MSV group performed 3 sets at a target weight (not-to-failure) and used loading variations producing heavy and light training days. All subjects in the MSV were instructed (and encouraged) to move the weight as explosively as possible. The variation in squat training intensity across 1 week allowed the MSV subjects to produce marked differences in velocity of movement in the squat. Data were analyzed using a repeated measures ANOVA. The alpha level was 0.05. Results showed that the 1RMS and CMVJ increased significantly over time (p Ͻ 0.05). The 1RMS improved 34.7% in the MSV and 24.2% in the SS. The CMVJ showed a significant interaction (p ϭ 0.047). The CMVJ improved 11.2% in the MSV and 0.3% in the SS. Body mass did not change significantly over time or between groups. These results generally show a superior adaptation for the MSV group. . Short-term performance effects of weight training with multiple sets not to failure vs. a single set to failure in women.