Objective: To investigate by comparing Human Chorionic Gonadotrophin (hCG) with Gonadotrophin Releasing Hormone Analogues (GnRHa) which induce the midcycle surge of LH and FSH by its flare-up effect for triggering ovulation. Study design: We followed up 29 cycles. The cycles were induced by clomiphene citrate (CC) or human menopausal gonadotrophin (HMG). We used buserelin acetate by intranasal route in 14 cycles (Group 1) and hCG 10.000 UI by intramuscular injection in 15 cycles (Group 2). In 7 cycles of group 1, 800 microgram buserelin acetate (Group 1A) and in other 7 cycles, 400 microgram buserelin acetate (Group 1B) was administered. The cycles were followed up by ultrasonography and hormonal parameters (LH, FSH, estradiol-E2, progesterone-P). Results: There were no differences between three groups (1A, 1B and 2) in terms of preovulatory LH, FSH, E2, P, E2 per follicle, numbers and diameters of follicles (> 14 mm) and endometrial thickness (p > 0.05). We detected the ovulation in 6 cycles of group 1A (85.7%), in 5 cycles of group 1B (71.4%) and in 13 of group 2 (86.7%). We could not find any significant differences between group 1A, 1B and 2 in terms of ovulation (p > 0.05). In addition the results were comparable between the group 1A and 1B as well (p > 0.05). Conclusion: We have believed that GnRHa which stimulate the endogenous LH and FSH surge in alternative to hCG for triggering ovulation.