The resumption of pituitary and ovarian activity was investigated by hormonal measurements and ultrasound scanning in 45 healthy post-partum women who were treated with bromocriptine. Bromocriptine, 50 mg (Parlodel LAR) was administered within 24 h post-partum. Plasma luteinizing hormone, follicle stimulating hormone, oestradiol, progesterone and prolactin concentrations were measured repeatedly and correlated with ultrasound measurements. Forty-one of the 45 women completed the study. A prompt fall in prolactin levels to normal (non-pregnant) values was observed within 24 h post-partum. Hereafter, a rapid return of the normal menstrual cycle was observed. Endocrine evidence of ovulation was obtained in 19/41 women within 1 month post-partum. Ultrasound measurements started at day 10 and were repeated regularly in 40 women. Ultrasound evidence of ovulation was found in 25/40 women. Ultrasound findings appeared not to correspond with the hormonal measurements. It is concluded that the resumption of pituitary and ovarian secretory functions post-partum is not always paralleled by a concomitant recovery of normal follicular growth and ovulation. Application of a progesterone threshold to judge resumption of ovulation post-partum should be reconsidered.