Squamous cell carcinoma antigen (SCC Ag) was estimated in 30 controls, in 16 patients with benign lesions of the uterine cervix, and in 51 patients with uterine cervical carcinoma. The rate of positivity of the antigen among the cancer patients was 87% (N = 49). SCC Ag estimations were of no diagnostic value, since 37% of patients with benign lesions had elevated levels compared to controls. SCC Ag was highly correlated to histologic subtype. The highest values were obtained in keratinizing tumors, followed by large cell nonkeratinizing and small cell nonkeratinizing types. Moreover, elevation of SCC Ag was statistically significant (p less than 0.001) among all the three histologic subtypes compared to controls. However, SCC Ag levels were not consistently correlated to the stage of the disease. Patients with pretherapeutic SCC Ag levels above 30 ng/ml had a faster recurrence rate and shorter survival than those who exhibited antigen values below 2.0 ng/ml. From our results, it is suggested that SCC Ag has limited use as a parameter for early diagnosis of cervical carcinoma, but it seems to reflect advancement of the disease. These findings indicate that SCC Ag elevation may prove to be a valuable marker in predicting subclinical disease.