Vascular endothelial growth factor (VEGF), an endothelium-specific growth factor and microvessel hypermeability factor, is expressed and secreted by several kinds of cells and is implicated in angiogenesis of tumors. The present study was performed to determine the relationship between the expression of VEGF in normal skin, benign and malignant epithelial lesions and cultured keratinocytes and the proliferative activity and degree of differentiation of keratinocytes. Skin lesions were studied immunohistochemically by staining with two anti-VEGF antibodies and secretion and production of VEGF by keratinocyte cultures were evaluated using an enzyme-linked immunosorbent assay. Low to moderate VEGF expression was observed in normal epidermis. In epithelial tumors, different reactivity patterns were observed and different areas of the same tumor expressed different amounts of VEGF. A more prominent labelling occurred in proliferative layers and/or more differentiated cells of virus-induced lesions, squamous cell carcinomas and Bowen's disease, whereas basal cell carcinomas always stained weakly for VEGF. In cultured keratinocytes, the amount of cell-associated and secreted VEGF increased with time, and the constitutively produced VEGF was mostly released extracellularly. High calcium concentrations upregulated the intracellular content of VEGF but downregulated its release. Taken together, these results showed a modulated expression and release of VEGF in relation to the stage of cell differentiation and in rapidly growing or activated keratinocytes.