SummaryAnovulation is the main cause of infertility in about one-third of infertile couples. It presents with amenorrhoea in about 40 per cent of cases, oligomenorrhoea in a further 40 per cent and luteal deficiency in about 20 per cent. Amenorrhoea is the absence of menstruation for at least 6 months between the ages of 16 and 40 years. Oligomenorrhoea is a menstrual interval greater than 6 weeks and less than 6 months. Luteal deficiency implies cycles of normal length, that is 3-6 weeks, but with inadequate luteal progesterone production.