In this paper are presented some chromatographic studies for partition of different molecular forms of prolactin (PRL), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in infertile women. Serum from three patients with prolactinoma and six with premature ovarian failure were fractionated in Sephadex G-100, and eighty fractions were collected, where PRL or FSH/LH were measured by radioimmunoassay, according with each case. Patients with prolactinoma showed two different chromatographic patterns for PRL. Two women with secondary amenorrhea and galactorrhea showed predominance of "little" PRL. In contrast, the patients with primary amenorrhea and galactorrhea showed only "big" PRL and "big-big" PRL. Among the patients with premature ovarian failure, two had chromosomal mosaicism, two had refractory ovarian syndrome and the other two had idiopathic premature ovarian failure. In these patients were found the presence of several molecular forms of FSH and LH, with different chromatographic profiles to those observed in normal young women and postmenopausal women. These results are indicating the presence of several molecular forms of pituitary hormones in patients with prolactinoma and premature ovarian failure.