Determinations of specific cytoplasmic receptors for 17 beta-estradiol (E), 5 alpha-dihydrotestosterone (DHT) and progesterone (P) in normal and abnormal endometrium are reported. The standardization of methodology with particular emphasis on specificity trials is outlined. Receptors were present in all but one case, a moderately differentiated endometrial adenocarcinoma. Generally speaking, steroid and peptide hormone plasma content in patients with malignant conditions were at the lower limit values of normal, except for follicle-stimulating hormone which had values significantly higher than normal. The question of E competition with DHT in binding DHT-receptor and the therapeutic implications of P-receptor estimation are discussed.