The aim of this study was to investigate the incidence of apoptosis in granulosa cells from immature human follicles undergoing in vitro maturation (IVM) and to compare the incidence of apoptotic granulosa cells (i) between FSH-primed and unprimed normal ovaries and (ii) between polycystic and normal ovaries. Furthermore, the incidence of apoptosis was related to maturation and subsequent fertilization and cleavage of the oocytes from the corresponding ovary. Seventy women undergoing 70 IVM cycles were included. Group 1 consisted of patients with normal ovaries (n = 52) and group 2 consisted of patients with polycystic ovaries (n = 18). Patients in group 1 were subdivided into two groups according to priming with FSH before aspiration. In group 1a (n = 27 cycles) oocytes were obtained in unstimulated cycles. In group 1b (n = 25 cycles) oocytes were obtained after priming with recombinant FSH for 3 days initiated on day 3 after spontaneous menstruation. In group 2 all patients were primed with recombinant FSH for 3 days before aspiration. Aspiration was performed transvaginally and cumulus-enclosed oocytes were matured for 28-30 h before fertilization. Granulosa cells were collected from follicular aspirates. An APOPTAG detection kit was used to stain the granulosa cells and to detect apoptosis. The incidence of apoptosis in granulosa cells was decreased in follicles from FSH-primed normal ovaries compared with follicles from unprimed normal ovaries and FSH-primed polycystic ovaries. No difference was found between granulosa cells from FSH-primed polycystic ovaries and granulosa cells from unstimulated normal ovaries. No differences in maturation rate, fertilization rate, cleavage rate and implantation rate were observed when oocytes from a polycystic ovary were compared with oocytes from an unstimulated normal ovary. In unstimulated cycles, the ovaries were grouped according to the presence of a dominant follicle. The incidence of apoptosis was significantly higher in granulosa cells from an ovary without a dominant follicle compared with granulosa cells from an ovary with a dominant follicle. The rates of maturation, fertilization and cleavage did not differ between the two groups.