The luteal phase (LP) of patients receiving triptorelin 0.1 mg to trigger ovulation was studied. Patients not pregnant in the first cycle with 0.1 mg were randomized into different groups for a second cycle: 0.1 mg again for patients who experienced a normal LP (group 1); patients affected with LP disorders were randomized into the following groups: 0.1 mg again (group 2); increasing dosage of triptorelin 0.5 mg once (group 3) or 0.1 mg three times (group 4); luteal support either with oral micronized progesterone (group 5) or human chorionic gonadotrophin (HCG) 1500 IU (group 6). Ovulation occurred in all cycles, but an inadequate LP was observed in 34.4% of the non-conceptional cycles. Patients demonstrating a normal LP as well as those affected with luteal disorders in their first cycle showed the same luteal pattern in their consecutive cycles triggered in the same way. In defective LP patients, increasing or repeating triptorelin doses did not restore the luteal phase or the pregnancy rate, both returning closer to normal after luteal support. Defective LP observed after agonist-triggered ovulation do not occur at random; therefore this patient-dependent response may be related to the personal characteristics of each patient's pre-ovulatory physiological surge profile.