Squamous cell carcinoma (SCC) antigen was first described 1977 by Kato et al. in patients with carcinoma of the cervix uteri. SCC serum levels can be measured with a radioimmunoassay (Abbott), in our investigation 2.0 ng/ml were taken as the upper limit of the standard range. In 35 healthy women there were no elevated SCC serum levels. In only 2 of 50 patients with benign gynaecological diseases SCC was also elevated. 59% of the 102 patients with primary and 70% of the 63 patients with recurrent cervical cancer showed pathologic values, CEA was elevated in 32% and 51% respectively; the mean serum concentrations increased with the stage of the disease. 68% of 142 patients with squamous cell carcinoma had elevated levels, in 5 of 9 adenosquamous carcinomas and in 3 of 14 adenocarcinomas SCC was in the pathological range. 13 of 60 patients with breast, endometrial and ovarian cancer showed elevated values. SCC shows a high specificity and a high sensitivity for squamous cell carcinomas of the cervix uteri. The tumor marker might be helpful in the control of the primary therapy and follow-up of cervical cancer patients.