From 1981-1991, 15 patients with primary fallopian tube carcinomas were treated at the University of Kentucky Medical Center. Immunohistochemical staining for CA-125 was performed on tumor specimens from all cases. Thirteen tumors (87%) stained positively for CA-125. Antigen staining was most intense in the apical portions of carcinoma cells. Serum CA-125 levels were measured in 5 patients and were elevated in 4 (80%). There was a positive correlation between tumor and serum antigen expression in these cases. Serum CA-125 levels accurately reflected disease status in the patients studied. These data suggest that CA-125 is a useful marker in patients with fallopian tube carcinoma. Immunohistochemical localization of CA-125 in tumor tissue should predict which patients will benefit most from serial antigen determinations.