Study Design Controlled laboratory study. Objectives To examine the effect of 2 adhesive tape conditions compared to a no-tape condition on muscle activity of the fibularis longus during a sudden inversion perturbation in male athletes (soccer, team handball, basketball). Background Ankle sprains are common in sports, and the fibularis muscles play a role in providing functional stability of the ankle. Prophylactic ankle taping with nonelastic sports tape has been used to restrict ankle inversion. Kinesio Tape, an elastic sports tape, has not been studied for that purpose. Methods Fifty-one male premier-league athletes were tested for functional stability of both ankles with the Star Excursion Balance Test. Based on the results, those with the 15 highest and those with the 15 lowest stability scores were selected for further testing. Muscle activity of the fibularis longus was recorded with surface electromyography during a sudden inversion perturbation. Each participant was tested under 3 conditions: ankle taped with nonelastic white sports tape, ankle taped with Kinesio Tape, and no ankle taping. Differences in mean muscle activity were evaluated with a 3-way mixed-model analysis of variance (ANOVA) for the 3 conditions, across four 500-millisecond time frames, and between the 2 groups of stable versus unstable participants. Differences in peak muscle activity and in the time to peak muscle activity were evaluated with a 2-way mixed-model ANOVA. Results Significantly greater mean muscle activity was found when ankles were taped with nonelastic tape compared to no tape, while Kinesio Tape had no significant effect on mean or maximum muscle activity compared to the no-tape condition. Neither stability level nor taping condition had a significant effect on the amount of time from perturbation to maximum activity of the fibularis longus muscle. Conclusion Nonelastic sports tape may enhance dynamic muscle support of the ankle. The efficacy of Kinesio Tape in preventing ankle sprains via the same mechanism is unlikely, as it had no effect on muscle activation of the fibularis longus. J Orthop Sports Phys Ther 2011;41(5):328–335, Epub 5 January 2011. doi:10.2519/jospt.2011.3501