To compare the oocyte and embryo quality and outcomes in polycystic ovary syndrome (PCOS) patients and normo-ovulatory women undergoing intracytoplasmic sperm injection (ICSI) cycles. We studied retrospectively 100 controlled ovarian stimulation cycles for ICSI in women with PCOS and 200 cycles in normo-ovulatory women. Every PCOS woman was paired according to age with two normo-ovulatory woman undergoing ICSI during the same study period. A long protocol of gonadotrophin releasing hormone (GNRH) agonist was carried out in all patients. The main outcome measures evaluated were: cancellation of the cycles, number of aspirated follicles, oocyte maturity, fertilization rate, embryo quality pregnancy and implantation rates, clinical abortion rate, multiple pregnancy rate and the "take-home baby" rate. Khi(2) test and Student t test were used for differences between normo-ovulatory and PCOS patients and the limit of significance was set at p<0,05. ICSI was performed for male infertility in most cases (79% in PCOS group vs 79,5%; NS). There was no significant difference in term of cancellation rate (5,5% in PCOS group vs 5%; NS). The mean number of follicles was higher in patients with PCOS (18,1+/-8,5 vs 9,4+/-5,5; p<0,001). Oocyte mature rate (67% vs 52%; p<0,001), fertilization rate (75% vs 63,7%; p<0,001) and grade 1 embryo rate (69% vs 53%; p<0,001) were significantly higher in PCOS group. The mean number of transferred embryos was similar in the two groups (2,46+/-0,5 vs 2,54+/-1,01; NS). Implantation rate (16,6% vs 12,1%; NS), clinical pregnancy rate per transfer (31,5% vs 24%; NS) and Live birth rate (22% vs 20%; NS) did not differ statistically in the two groups. Twin and triplet pregnancies rates were similar in the two groups (20% vs 16,7%; NS and 6,6% vs 7,1% ; NS respectively). Miscarriage rate was higher in PCOS group but this did not reach the statistical significance (26,6% vs 16,6%; NS). PCOS patients showed better global oocyte and embryo quality. However, pregnancy and live birth rates were similar in the two groups when number and quality of transferred embryos are equivalent.