Human luteal phase function as evaluated by peripheral venous blood steroid levels does not appear to be impaired following the aspiration of follicular fluid together with a cumulus enclosed oocyte and a number of granulosal cells from the immediate preovular follicle in women having otherwise spontaneous ovular cycles. The day to day levels of luteinising hormone, oestradiol-17 beta, 17 alpha-hydroxy-progesterone, progesterone and basal temperatures in 14 women who had their preovular follicle aspirated were compared with a control group of 28 spontaneously ovulating women. It was concluded that a carefully performed single aspiration of the contents of a preovular follicle, for the purpose of extra-corporeal fertilisation of the mature oocyte, did not lead to impaired steroid function of the subsequent corpus luteum, although the prolactin levels were increased due to the effects of the relaxant anaesthetic and/or the laparoscopic procedure. A safe and simple laparoscopic procedure is also described, which is particularly suitable for women with a likelihood of extensive pelvic adhesions.