Vascular endothelial growth factor (VEGF) is a previously discovered angiogenic factor that seems to influence the neoangiogenesis of neoplastic and non-neoplastic tissues. Substantial experimental evidence links tumor growth and metastasis with blood vessel formation. Tumor angiogenesis can be induced by factors released by the tumor cells themselves. A variety of transformed cell lines expresses the VEGF transcript and secretes an EGF-like protein, suggesting that this angiogenic factor may be one of the mediators of tumor angiogenesis. By Northern blot analysis and in situ hybridization, we investigated the expression of VEGF transcript in human ovarian and endometrial neoplasms. Messenger RNA encoding VEGF was detected in all tissues studied and was more densely expressed in endometrial carcinoma. VEGF expression was also identified in cells obtained from ovarian and endometrial ascitic fluid. VEGF mRNA, detected by in situ hybridization, was identified in the epithelial cells of endometrial adenocarcinoma. This distribution was localized primarily in the apices of the papillae. The prominence of VEGF mRNA levels in human ovarian and endometrial tumors demonstrates that VEGF may be involved in promoting tumor angiogenesis and stroma generation, acting as an endothelial cell mitogen.