With the use of pelvic ultrasound imaging we have found that more than half of the women presenting to our clinic with ovulatory disturbances have polycystic ovaries. As a group hirsutism is common, the serum LH, the LH:FSH ratio and serum androgen levels are higher than in other groups of patients with anovulation, but many of the women we studied were non-hirsute and had normal levels of these hormones. The aetiology of PCOS remains obscure and there is probably more than one cause. Disturbance of hypothalamic/pituitary, ovarian or adrenal function could all result in the development of polycystic ovaries. Our own data, based on pelvic ultrasound and measurement of serum androgen levels, suggest that an ovarian abnormality, other than the obvious morphological one, may be identified in most women although this does not prove (except perhaps in those women with unilateral PCOS) that the ovary is the primary site of the disturbance. Management of ovulatory disturbances includes symptomatic treatment of dysfunctional uterine bleeding and induction of ovulation. Although the ovulation rate following clomiphene is quoted as about 75%, this is probably an overestimate; less than half the 'ovulators' become pregnant and in those who do there is a high risk of early pregnancy loss. Induction of ovulation in clomiphene non-responders remains a difficult problem. The results of ovarian wedge resection are variable and any beneficial effect is short-lived with the risk of long-term infertility due to pelvic adhesions. Laparoscopic electrocautery may be a useful alternative, but it is too early to assess this form of treatment. Of the medical methods of ovulation induction in clomiphene non-responders, two methods have emerged as being highly promising: the first is administration of HMG following suppression of the pituitary by an LH-RH analogue; so far only a very small number of patients have been treated. The second is low-dose FSH. Initial studies, including our own, have shown a high incidence of ovulation and a pregnancy rate of 50%.