© 2015 Human Kinetics – IJATT. Context: Hamstring injuries are prevalent among team and field sport athletes, and poor flexibility has been theorized as a risk factor. The active knee extension test has been proposed as the gold standard for assessment of hamstring flexibility. Many variations of this test are employed, each of which utilizes a complex apparatus that is difficult to transport, time-consuming to set up, and often unavailable to most clinicians. Thus, a method that utilizes inexpensive and readily available equipment is needed for screening. Objective: To establish the intertester and intratester reliability of a modified active knee extension test that requires minimal equipment. Design: Reliability study. Setting: Athletic therapy facilities. Patients or Other Participants: Fifteen male athletes (19.5 ± 0.6 years) free from any orthopedic or neurological disorders were recruited from a convenience sample of collegiate students. Intervention(s): Three testers participated in three training sessions before data collection. Participants completed three trials of the modified active knee extension test and returned the following week at the same time and day to repeat the process. Main Outcome Measure(s): The intraclass correlation coefficient (ICC), 95% confidence interval, and the standard error of measurement were calculated to assess inter-and intratester reliability. Results: High ICC values were found for intertester reliability (right leg =.98; left leg =.99) and intratester reliability (right leg =.78–.89; left leg =.79–.94). Conclusions: The modified active knee extension test utilizes readily available equipment and offers a quick, reliable, and low-cost alternative for measurement of hamstring flexibility.