The aim of the study is to investigate the acute effect of active static stretching on isokinetic leg strength and change of this effect depending on resting after stretching in athletes. 23 male and 38 female athletes from various branches (22-football, 19-volleyball, 16-basketball and 4athletics) participated in the volunteer work at Gazi University Faculty of Sports Sciences between ages 19-23. Four separate active static stretching exercises for hamstring, quadriceps, and other muscles of right knee for sixty seconds each were identified. Participants were administered four different protocols involving the these exercises [(a) warming, (b) warming+static stretching, (c) warming+static stretching + five minutes rest, (d) warming + static stretching+fifteen minutes rest) then hamstring and quadriceps isokinetic strength and hamstring/quadriceps isokinetic strength ratio H/Q (R) values were recorded at 60 o /sec angular velocity using the Isomed after each protocol. Statistically significant results were obtained between the a-b and b-d measurements as a result of the analyzes. In both male and female and total (T) analyzes; compared with (a), (b) measurement values were significantly lower (T; hamstring;a-b=+17.8 Nm, quadriceps;a-b = +19.6 Nm) and (d) measurement values were significantly higher when compared to (b) (T; hamstring;b-d=-13.7 Nm, quadriceps;b-d=-14.3 Nm).There were no significant differences between other measurements and power ratios (H/Q) (p<0.05). It is suggested that the acute static stretching has a negative effect on the isokinetic strength of the muscle by findings, so it is advisable to terminate the static stretching at least fifteen minutes before the competition or to avoid activities requiring maximum contraction immediately after active static stretching. On the other hand, different stretching times, different angular velocities and the need for new work to be done with different muscle groups should not be overlooked.