The prognosis of patients with carcinoma of the uterine cervix has been shown to depend on the oxygenation and vascularization status of the tumors. The purpose of the study reported here was to search for possible differences in oxygen tension and vascular density between adenocarcinomas and squamous cell carcinomas. Ten patients with adenocarcinoma and forty patients with squamous cell carcinoma were included in the study. Oxygen tension was measured polarographically using the Eppendorf pO2 Histograph 6650. Vascular density was determined by histological examination of tumor biopsies. The adenocarcinomas were significantly better oxygenated than the squamous cell carcinomas. The squamous cell carcinomas and the adenocarcinomas did not differ significantly in vascular density. The difference in prognosis between patients with adenocarcinoma and patients with squamous cell carcinoma is probably not attributable to differences in tumor oxygenation or vascularization.