Autoimmune (lymphocytic) hypophysitis has emerged as a distinct and specific clinical and pathological disease entity. Although relatively rare compared with other autoimmune endocrine diseases, nearly a hundred cases have been described. The condition is much more common in females (9:1) and appears to have a particular predilection for the pregnant and postpartum states. The anterior pituitary, and less often the neurohypophysis, appear to be the target for inflammatory autoimmune destruction. During the evolution of the disease process, pituitary hyperfunction (usually hyperprolactinemia) has been noted. This disease should now be included in the differential diagnosis of pituitary disorders, especially in females presenting with pituitary enlargement, particularly if symptoms occur in temporal relationship to pregnancy. The disease may form part of the spectrum of the polyglandular autoimmune endocrine disorders. (Trends Endocrinol Metab 1997;8:74-80). (c) 1997, Elsevier Science Inc.