The purpose of the study was to evaluate the acute effects of static stretching, proprioceptive neuromuscular facilitation (PNF), and active isolated stretching (AIS) on one-repetition maximum knee flexion in college students. We hypothesized that stretching would inhibit one-repetition maximum knee flexion, and that AIS would affect the lift less than static stretching or PNF. Subjects were 41 male and 21 female volunteers from local colleges. Subjects were randomly assigned to one of three experimental groups or a control group. Subjects in the experimental groups performed one of the three specified stretching treatments, focusing on the knee flexors. Subjects were tested for one-repetition maximum knee flexion 4 days prior to treatment, immediately after treatment, and 3 days after treatment. One-repetition maximum was assessed using a plate-loaded leg curl machine. The score used for analysis was the last successfully completed attempt following ACSM test guidelines. Data were analyzed using a two-way mixed model ANOVA. ANOVA yielded a significant main effect for time (F1, 62 = 21.04, p < .001), however, Tukey's HSD failed to indicate the source of the differences. There was also a significant group X time interaction (F2, 62 = 8.22, p < .001). A plot of the means revealed that the interaction was caused by an increase in one-repetition maximum in the control group during the immediate test period, while the other three groups all had a decline in one-repetition maximum during this period. Both significant findings had large effect sizes, eta2 = .43 and .30, respectively. The group X time interaction suggests that stretching may create a short-term inhibition of one-repetition maximum strength performance. The greatest decline in performance was observed in the static stretching group and the least was in the AIS group. While no differences in one-repetition maximum knee flexion were observed between AIS and the other stretching protocols, the smaller decline in performance after AIS was in the direction of our second hypothesis. Further research into the effects of stretching prior to strength performance should attempt to quantify the magnitude of the possible stretching inhibitory effect.Keyword(s): athletics/sports, exercise/fitness, performance