Binding sites of peanut agglutinin (PNA), Ulex europaeus (UEA-1), wheat germ agglutinin, concanavalin A, and Ricinus communis were localized in 46 common epithelial ovarian tumors. Binding pattern of serous cystad-enomas showed significant similarity with the pattern seen in the epithelium of fallopian tubes. Lectin affinity of endometriosis and endometrioid tumors was similar to normal endometrium in secretory phase. Binding pattern of clear cell carcinomas was similar to gestational endometrium, with PNA and UEA-1 showing strong affinity. This pattern is in contrast to clear cell carcinomas of the kidney, that do not bind PNA and UEA-1. Mucinous cystade-nomas exhibited binding patterns identical with cervical epithelium. Malignant counterparts of the described tumors were characterized by the partial loss of lectin binding and uneven distribution of the binding reaction.