Abstract Twenty-four-hour urine samples from known gynecologic cancer patients and normal donors were tested for antigen by a complement fixation assay using autologous sera as antibody sources. Eleven of fourteen cancer patients (78.6%) were antigenically positive while only 1 of 9 (11.1%) normal donors was positive. Absorption of sera with autologous tumor cells removed the antibodies while uninvolved gynecologic tissues were ineffective as absorbents. In 1 patient whose disease was surgically debulked, removal of the tumor was characterized by a diminution in antigen excretion.