To compare the fertilization rates and pregnancy rates (PRs) in intracytoplasmic sperm injection (ICSI) using sperm from ejaculates of normal and abnormal semen, epididymal sperm, and testicular sperm of obstructive and nonobstructive azoospermic patients. Retrospective study. The Egyptian IVF-ET Center. Three hundred fifty patients underwent 366 ICSI cycles. ICSI, epididymal sperm aspiration, and testicular biopsy. Fertilization rates and PRs. Patients were divided into five groups according to the quality and source of sperm. Patients in group 1 underwent 102 cycles of ICSI using ejaculated abnormal semen, group 2 underwent 44 cycles using epididymal sperm, group 3 underwent 82 cycles using testicular sperm from obstructive azoospermia, group 4 underwent 80 cycles using testicular sperm from nonobstructive azoospermia, and group 5 underwent 58 cycles using normal semen. There was no significant difference in the fertilization rates and PRs among groups 1, 2, and 3. In group 4, the fertilization rate and PR were significantly lower than in all other groups. In group 5, the fertilization rate was significantly higher than in all other groups. The fertilizing ability of sperm in ICSI is highest with normal semen and lowest with sperm extracted from a testicular biopsy in nonobstructive azoospermia. There was no significant difference in fertilization rates and PRs between ejaculated sperm of different parameters and surgically retrieved sperm in obstructive azoospermia.