The immunohistochemical localization of Laminin has been investigated with a monoclonal antibody in biopsy specimens from 27 patients with an invasive squamous cell carcinoma of the oral cavity. In normal mucosa, laminin was found distributed in a linear pattern in the epithelial-stromal junction, around the blood vessels, the nerve fibres, and the skeletal muscle bundles. In the cancerous tissues a variety in the linear staining around the cancer cell nests was seen. Extreme attenuation or complete loss of the linear staining of laminin was demonstrated in 8/27 specimens, and these tumors histologically showed a high grade of malignancy with H.E. staining.