Several indirect clinical tests for measuring hamstring muscle length are available, but the influence of their test procedures is not well documented. This study examined four of these tests to clarify the results relative to the testing procedures. The right limbs of 30 men were tested for: 1) passive straight leg raise (SLR) with the pelvis and opposite thigh stabilized with straps (SLR-SS); 2) passive SLR with the low back flat and, if needed, the opposite thigh slightly flexed and supported on pillows (SLR-LBF); 3) active knee extension with the hip at 90 degrees (AKE); and 4) passive knee extension with the hip at 90 degrees (PKE). A dependent t-test showed no significant differences between the angles of SLR-SS (61 degrees +/- 6.7 degrees) and SLR-LBF (62 degrees +/- 6.2 degrees). The SLR-SS and SLR-LBF angles for subjects needing pillows under the opposite thigh for the SLR-LBF test (N = 18) also were not significantly different. The knee flexion angles for the AKE (43 degrees +/- 10.2 degrees) and the PKE (31 degrees +/- 7.5 degrees) tests were significantly different (p < 0.001). Significant relationships (Pearson r) were found among the four tests (p < 0.05). The similar angles for SLR-SS and SLR-LBF and their significant relationship (r = 0.70, p < 0.001) indicated that their different testing procedures probably had a minimal influence on test results. The difference between the AKE and PKE tests suggested that the AKE test and the PKE test may represent an "initial length" and a "maximal length," respectively.(ABSTRACT TRUNCATED AT 250 WORDS)