This research was conducted to investigate the interrelationship among methods of injection of PMSG-hCG to the number of ovulated eggs, percentage of matured oocytes and in vitro fertilization using out-bred ICR mice. The results obtained are as follows, 1) The optimurn dose was 5 IU for both PMSG and hCG, while the number of ovulated eggs was 42$pm$8, percentage of M II was 73% and in vitro fertilization rate was 81 %. 2) The optimum injection interval of PMSG-hCG was 48 hours, while the number of ovulated eggs was 48 $pm$ 8, percentage of M II was 80% and in vitro fertilization rate was 81%. 3) The optimum time for collecting eggs was between 16 and 18 hours after hCG injection, while the numbers of ovulated eggs were 44$pm$8, 42$pm$7 and 43$pm$7 in 14,16 and 18 hours after hCG injection respectively, and percentages of M II were 79 and 81 %, and in vitro fertilization rates were 81 and 80% in 16 and 18 hours after hCG injection, respectively. 4) The repeat of superovulation decreased with the number of ovulated eggs, percentage of M II and in vitro fertilization rate, than in control. But it was recovered by increasing the repeat interval.