Résumé : Objective: To analyze the occurrence of deliveries after spontaneous conception in patients who have discontinued unsuccessful intracytoplasmic sperm injection (ICSI) treatment. Design: Cohort follow-up study.Setting: Tertiary referral center. Patient(s): Between July 1992 and December 1993, 200 Belgian women younger than 37 years underwent 433 consecutive unsuccessful ICSI cycles with freshly ejaculated sperm and eventually discontinued their treatment.Intervention(s): Ultrasound-guided oocyte retrieval and ICSI. Main Outcome Measure(s): Delivery after 25 weeks following a spontaneous pregnancy. Result(s): The mean age at the time of the last oocyte pick-up was 31.0 ± 3.9 years. The mean time interval between the last ICSI and the end of the follow-up period was 47.7 ± 12.1 months. Twenty-three spontaneous pregnancies ending in delivery after 25 weeks were observed (11.5%). The cumulative delivery rate reached a plateau of 10% after 36 months of follow-up. The mean time interval (from last oocyte retrieval) for spontaneous pregnancy to occur after discontinuing ICSI treatment was 20.2 ± 13.7 months. Proportional hazards analysis showed that delivery rate was reduced by 2.0% per year of infertility. Conclusion(s): This study suggests that duration of infertility appears to be predictive of the likelihood of live delivery after spontaneous conception following an unsuccessful ICSI treatment. Copyright © 2002 American Society for Reproductive Medicine.