Seventy-seven women with clinical suspect of microprolactinoma were studied by means of magnetic resonance of the pituitary gland. The homogeneity and signal intensity of the pituitary gland, presence of intraglandular nodule, height and gland morphology were evaluated. Radiological findings were correlated to prolactinemia values and the definite clinical diagnosis. The pituitary gland was normal in eleven out of the thirteen patients in whom the presence of hypophyseal endocrine pathology was not confirmed. In the remaining 64 women with hyperprolactinemia, 26 hypophyseal nodules were detected (40.6%), 3 questionable nodules (4.7%), 8 homogeneous glands (12.5%), 6 of empty sella turcica (9.4%) and 21 normal pituitary glands (32.8%). A correlation between radiological diagnosis, prolactinemia levels and definite clinical diagnosis was verified. The convexity degree of the pituitary gland was not useful for the diagnosis of microprolactinoma. In contrast, the height of the pituitary gland was indeed useful.