Squamous cell carcinoma (SCC) antigen was described as being associated with malignant disease of the uterine cervix, and was determined by a radioimmunoassay technique. We studied squamous cell carcinoma serum levels in 72 patients from our gynecological clinic. Forty-three were diagnosed as having gynecological malignancies, and 29 as having benign diseases. The malignant disease group included 35 carcinomas of the uterine cervix, 7 endometrial cancers, and 3 vulvar cancers. Gynecological cancers were classified according to the FIGO system. We also determined SCC levels among 69 healthy subjects. Results showed that 97.1% of healthy subjects were below the cut-off point, 2.5 micrograms/l. Patients with benign gynecological diseases had increased SCC levels in 5.9% of cases. Among gynecological cancers, 56% of 23 cases of cervical cancer and one of three vulvar cancer, all of them in the active phase, had increased levels. The nine squamous carcinomas of the cervix with no evidence of disease, as well as seven endometrial adenocarcinomas with active disease were negative. Thirty-three percent of 12 cervical cancers in Stages I and II were high levels, compared to 81% of 11 advanced stages; none of the 2 early stage carcinoma of the vulva, but 1 advanced stage were increased. SCC is clinically applicable to monitor size and tumor volume of carcinomas of the uterine cervix derived from squamous epithelium.