From 1 October 1991 until 31 December 1993, 1270 cycles for intracytoplasmic sperm injection were performed. Of these, 71 (5.6%) were carried out in women >/=40 years of age. The semen characteristics in couples >/=40 years of age or <40 years were similar. The mean male age for the older group of women was 47.1 years (range 34-67) versus 35 years (25-71) for the younger group of women (P < 0.001). The mean female age was 41.9 years (range 40-47) and 31.8 years (range 23-39). The numbers of cumulus-oocyte complexes and metaphase-II oocytes were significantly lower in women >/=40 years of age (P < 0.001). The mean numbers of replaced embryos were respectively 2.3 (133/59) in women >/=40 years of age and 2.5 (160/63) in women <40 years of age. The delivery rate per retrieval and per transfer was significantly lower in women >/=40 years of age (P < 0.05). The delivery rates per retrieval and per transfer were respectively 7% (5/71) and 8.5% (5/59) in the older group of women versus 22.5% (16/71) and 25.4% (16/63) in the younger group. Female age is the predictive factor for embryonic implantation.