In this study the importance of Intrafollicular prolactin (PRL) and sex steroid levels, as indices of the potential invitro fertilization and development of human oocytes, was investigated. Oocytes were recovered from 20 normal female volunteers treated with a fixed schedule including norethisterone and clomiphene. The embryos which developed after in-vitro fertilization were graded on a scale of 0 to 10 using morphological criteria. Intrafollicular PRL, oestradiol, progesterone and androstenedione levels did not differ significantly between follicles containing oocytes which fertilized and those which did not fertilize in vitro. Nor did these hormones differ significantly between follicles giving rise to embryos with a bad score (0–5) and those with a good score (6–10). No significant correlation was found between serum and follicular fluid PRL levels. It is suggested that fertiliza tion and developmental potential of human oocytes in vitro cannot be predicted by the intrafollicular levels of PRL and sex steroids at the time of laparoscopic egg recovery.