Increased microvessel density has been described in squamous cell carcinoma of the head and neck and is related to patient prognosis. The factors responsible for the angiogenesis have not been identified. Vascular permeability factor (VPF), also known as vascular endothelial growth factor (VEGF), is a multifunctional angiogenic cytokine expressed at high levels in many tumors. We examined 16 cases of squamous cell carcinoma, 10 cases of high-grade squamous dysplasia, and 19 cases of normal, reactive, or mildly dysplastic squamous mucosa by in situ hybridization for expression of VPF/VEGF and VPF/VEGF receptor mRNA. Strong expression of VPF/VEGF mRNA was seen in 12 of 16 squamous cell carcinomas and in 5 of 10 high-grade squamous dysplasias. In contrast, no cases of normal, reactive, or mild dysplastic squamous epithelium showed strong expression of VPF/VEGF mRNA. Furthermore, strong expression of VPF/VEGF receptor mRNA was seen in 5 of 9 cases of squamous cell carcinoma and 3 of 6 cases of high-grade squamous dysplasia but in only 2 of 14 cases of normal, reactive, or mild dysplastic squamous epithelium. Thus, expression of VPF/VEGF and its receptors is markedly increased in high-grade squamous dysplasia and invasive squamous cell carcinoma of the oral cavity and larynx and may play an important role in the angiogenesis associated with these lesions.