This paper reports an analysis of the clinical, endocrine and ultrasound data within a population of 556 patients with ultrasound-diagnosed polycystic ovaries. Compared with those not so affected, hirsutism was associated with a higher mean serum testosterone concentration, infertility was associated with higher mean gonadotrophin concentrations, obesity was associated with a higher mean serum testosterone concentration, hyperprolactinaemia was associated with a lower mean serum testosterone concentration and smaller ovaries, alopecia was associated with lower mean serum LH and testosterone concentrations, and acanthosis nigricans was associated with obesity and a raised mean serum testosterone concentration. The heterogeneity illustrates the limitations in the use of specific clinical or endocrine criteria as requirements for the diagnosis of the polycystic ovary syndrome.