AbstractAn in vitro fertilization system utilizing squirrel monkeys was used to compare follicle‐stimulating hormone, clomiphene citrate and prostaglandin E1as follicular induction regimens, analyze culture medium characteristics, and examine the physiological phenomenon of polyspermy. Induction of follicular growth was poor with clomiphene citrate when compared to the control group and increased the incidence of atretic follicles at all levels tested. When prostaglandin E1was administered, larger numbers of mature oocytes were recovered at laparoscopy. There was no difference in fertilization rate between the treatment and control groups.Homologous serum was an adequate protein source in TC‐199 fertilization medium for squirrel monkey oocytes. Although the rate of triploidy was increased with in vitro fertilization, there was no relationship between sperm concentration and the incidence of polyspermy. These findings demonstrate that the squirrel monkey is a valuable primate system for studies of in vitro fertilization and preimplantation development. © 1993 Wiley‐Lis