Angiogenesis, the induction of new capillaries and venules, has been associated with tumor growth. Increased tumor size and new vessel growth may further the opportunity for tumor cells to enter the circulation and potentiate metastatic disease. To investigate if tumor angiogenesis could serve as a prognostic factor in cervical carcinoma, we counted microvessels (capillaries and venules) in 29 patients with squamous cell carcinoma of the cervix. Surgical specimens were stained for endothelial cells specifically with Factor VIII to identify all vessels. The microvessels were counted by light microscopy (per 200 x field) in tumor sections with the highest population of microvessels. This was performed by two investigators without knowledge of patient outcome or extent of disease. Microvessel counts in patients with squamous cell carcinoma were significantly different from those of control subjects: 56 +/- 28.9 and 16.3 +/- 3.3 (P = 0.013). There was no correlation between microvessel count and node status, parametrial involvement, depth of invasion, or gross disease. Microvessel count was significantly correlated with vascular space involvement (P = 0.017). Four patients who developed recurrent disease within 1 year had high microvessel counts and yet were node negative and VSI negative at surgery. As shown by Folkman in breast cancer, angiogenesis may also be an independent predictor for recurrent disease in squamous cell carcinoma of the cervix. Microvessel counts could be of prognostic value in patients who do not have other risk factors for disease recurrence.