This investigation determined the effects of a static stretching program with different stretching protocols on the flexibility and passive resistance of the hamstrings of young adults. Forty healthy subjects (24 males and 16 females) aged 18 to 30 years were randomly assigned to one of four groups. The two training groups underwent static stretch training of the hamstrings either with a four-week protocol or with an eight-week protocol. The other two groups acted as control groups. A significant increase in flexibility of hamstrings was found in both of the two training groups (P<0.05). No difference was found in the range of motion gained between the two training groups. An increase in passive resistance at the corresponding maximal joint angle was only demonstrated in the four-week training group (P<0.05). Both protocols are effective in terms of improving flexibility of hamstrings. However, if injury is reduced when there is relatively lower passive resistance at the end-of-range, then the eight-week training regimen would be recommended.