OBJECTIVE Our objective was to compare the fertilization rates achieved by ICSI versus SUZI in couples with severe male infertility. METHODS This was a randomized, prospective study. METHODS The study took place at the In-Vitro Fertilization-Embryo Transfer Unit, Department of Obstetrics and Gynecology, The Chaim Sheba Medical Center. METHODS Oocytes of 12 patients were randomly allocated to either ICSI or SUZI procedures. Each woman thus served as her own control. All 12 patients had undergone at least two previous in vitro fertilization cycles with no fertilization or had a very low sperm count, i.e., a total motile sperm count of less than 0.5 x 10(6). RESULTS A total of 117 oocytes was obtained for fertilization. Of these oocytes, 16% (10/63) were successfully fertilized by SUZI, compared to 33% (18/54) treated by ICSI. This difference was statistically significant (P < 0.05). Of the 12 cycles, ICSI provided embryos in 10 cycles (83%), while SUZI was successful in only 6 cycles (50%). Four pregnancies were achieved: 33% per attempt, or 40% per transfer.