A well documented sporadic case of multiple endocrine adenomatosis (MEA) type I, with the pituitary tumour presenting as a prolactinoma, is described in a 28-year-old female. Primary amenorrhoea, resulting from hyperprolactinaemia, was the first symptom of the polyglandular neoplasia. A gastrinoma was removed from the head of the pancreas and latent hyperparathyroidism appeared to be present. Treatment with bromocriptine was poorly tolerated; neurosurgical intervention was refused by the patient. The possibility that a serum prolactin determination may be useful in detecting pituitary involvement in MEA deserves consideration.