To reduce the number of animals required for controlled,studies of marmoset oocytes and early embryos, a superovulation protocol was developed for the common marmoset. Females were given up to 50 i.u./day recombinant human follicle stimulating hormone (FSH) - (r-hFSH) for 6 days. Ovaries were visualized by a modified laparoscopic technique and follicular aspiration was performed using a needle and suction apparatus inserted directly through an otoscope speculum. The number of follicles + ovulation points (+/- S.E.) was 2.9 (+/- 0.2) in controls and 14.1 (+/- 1.6; P less than or equal to 0.001) in the 50 i.u. r-hFSH per day animals. Oocytes, typically at the germinal vesicle stage at collection, extruded a first polar body within 26 hours. In vitro fertilization was performed and embryos developed to the hatched blastocyst stage (34%). With many high quality oocytes and the ability to synchronize cycles, the marmoset is a valuable primate model for examining nuclear reprograming and early embryonic events.