Hamstring strains are a common athletic injury with a tendency to recur. Lack of flexibility has been suggested as a predisposing factor to hamstring strains. Clinicians have generally considered flexibility training to be an integral component in the prevention and rehabilitation of injuries, as well as a method of improving one's performance in daily activities and sports. As clinicians, we often provide stretching protocols to athletes with the expectation that flexibility gains will last long enough to have at least a temporary beneficial effect. For athletes to take advantage of flexibility gains, it would be useful to know how long these effects last. For example, the athlete who performs a series of static stretches and then attends a team meeting or sits on the sideline for 30 minutes may not retain the effects of stretching when practice begins or upon entering a contest. Previous research examining the hamstring complex has shown that stretching increases one's range of motion, regardless of whether the stretching technique performed is ballistic, static, proprioceptive neuromuscular facilitation, or modified proprioceptive neuromuscular facilitation techniques. However, only 3 of these studies measured how long the hamstring gains were maintained, and all 3 assessed gains after multiple-day stretching programs. No study has addressed the duration of flexibility gains immediately after cessation of a single, same-day series of acute static stretches. Thus, the purpose of our study was to measure the duration of hamstring flexibility gains after cessation of a same-day static stretching protocol.