Aim of the study is to find out the effect of extensive and intensive interval training on flexibility among athletes. A pretest-posttest randomized group design was used for this study. The randomly selected (N=60) college men athletes from Andhra Pradesh were divided into three groups randomly consisting of twenty college men athletes in each. Before the training pre test was taken for all the groups on flexibility. Experimental group I underwent extensive interval training, experimental group II underwent intensive interval training for twelve weeks. The control group did not undergo any type of training. At the end of twelve weeks the post test was conducted on flexibility. The difference between initial and final test scores was considered as the effect of respective training on selected criterion variables. to test the significance of the obtained data were subjected to statistical measures using ANCOVA. In all cases 0.05 level was fixed to test the hypothesis for this study.