A total of 10,550 'normal' adults (8450 men and 2100 women) in the general population were screened by a paired assay method for serum PRL and 40 subjects with hyperprolactinaemia (greater than 75 micrograms/l) were detected. Of these, five patients (three men and two women) with pituitary prolactinoma, one man with empty sella syndrome, 10 cases of 'big' prolactinaemia, seven pregnant women and 13 subjects with drug-induced hyperprolactinaemia were found. The patients with prolactinoma had few if any complaints (asymptomatic prolactinoma).