Angiogenesis has been linked to increased metastasis formation and decreased overall survival in patients with various tumors, including and neck squamous cell carcinomas (HNSCC). Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis. In the present study, we evaluated VEGF expression and microvessel density (MVD), a quantitative means of angiogenesis, in both experimental and clinical models of HNSCC. Analysis of VEGF RNA expression in cell lines of keratinocyte origin [HNSCC, facial skin squamous cell carcinoma (SCC), and transformed but nontumorigenic keratinocytes] and normal skin keratinocytes revealed two VEGF transcripts corresponding to proteins of 165 and 121 amino acids in length, with the transcript for the 165-amino acid species predominating. Six of eight SCC cell lines showed increased levels of one or both transcripts, and seven SCC cell lines and the transformed keratinocyte cell line showed increased protein expression. We then evaluated VEGF protein expression in human head and neck specimens containing normal epithelium (n = 10), dysplasia or carcinoma in situ (CIS; n = 15), early invasive SCCs (n = 9), advanced primary SCCs (n = 10), lymph node metastases (n = 3), and s.c. tumors or cysts (n = 7) formed in severe combined immunodeficient mice. Intense VEGF staining was found in the majority of advanced primary SCCs, lymph node metastases, and human SCCs in severe combined immunodeficient mice, whereas no dysplasia, CIS, or early SCCs showed intense immunostain. A highly significant increase (P = 0.0001) in VEGF expression was seen in the advanced SCC versus dysplasias and CIS lesions, as was the difference between SCC versus normal epithelium from nonsmokers (P = 0.01). VEGF expression in advanced primary cancers was greater (P = 0.002) and, in early cancers, marginally greater (P = 0.05) than adjacent normal mucosa. MVD increased with the progression of preinvasive disease (P = 0.04). VEGF expression and MVD (both, P = 0.003) were directly associated with tumor aggressiveness in experimental tumors. These findings suggest a role for VEGF in both clinical and experimental HNSCC.