PURPOSE: To analyze cumulative and single-cycle success rates of IVF and intracytoplasmic sperm injection (ICSI) separately in relation to female age, fertilization modality, and first-cycle outcome. METHODS: The study involved 2997 patients and couples, respectively, who underwent 5339 fresh and 3006 cryo cycles using pronuclear-stage oocytes. Fertilization was achieved by the conventional IVF or ICSI. Because of legal restrictions in Germany, no embryo selection was performed. All cycles were documented prospectively. Kaplan-Meier survival rates were calculated for all treatment cycles and transferred embryos. RESULTS: Essentially, the success of assisted reproductive technology (ART) depends on a woman's age and on skilful counselling. Cumulative pregnancy and live-birth rates are the best indicators of successful ART. Probably for the first time, we determined these cumulative rates separately for IVF and ICSI, and found them to be almost identical. Live-birth rates reached 70-95 %, except for women aged over 40 years, whose chances of life birth are limited to about 25 %. Live-birth rate per retrieval was 25.61 % for IVF and 26.3 % for ICSI. Time to pregnancy was shorter for women who underwent a successful treatment in their first cycle. CONCLUSIONS: The primary intention for the choice of fertilization modality between IVF and ICSI is the prevention of a relative or total fertilization failure. Such treatment failure is best prevented through ICSI, which results in slightly higher clinical pregnancy rates per started cycle. After embryo transfer, there are no differences in the success rates of IVF and ICSI. The supposed cumulative live-birth rates are useful as a basis for counselling subfertile couples to help reduce the high discontinuation rate, which is still the main reason for inefficacy in ART. Following an unsuccessful first treatment cycle, the prognosis remains positive, but until success is achieved, more treatment cycles are necessary.