The distribution of the basement membrane anchoring fibril component type VII collagen was studied in oral squamous cell carcinoma by using in situ hybridization and immunohistochemical methods. The expression of type VII collagen in oral normal mucosa, lichen planus and epithelial dysplasias was also investigated. In squamous cell carcinomas, the signals for type VII collagen mRNA were located exclusively in malignant peripheral cells in tumour islands and in fibroblast-like cells among the stromal tissue. In normal buccal mucosa, type VII collagen mRNA expression was located in basal epithelial cells. In oral lichen planus and epithelial dysplasias, the signals for type VII collagen mRNA were also located in basal keratinocytes; however, the signal was especially strong in some epithelial cells. In oral squamous cell carcinomas, the linear immunohistochemical staining pattern of type VII collagen was noted surrounding partly squamous epithelial tumour cell islands, and a large number of tumour cells showed a cytoplasmic staining reaction using the type VII collagen antibody. Some fibroblast-like stromal cells also showed a positive immunostaining reaction. In conclusion, the results of this study indicate that a high synthesis level, but an impaired distribution of type VII collagen, are highly characteristic of squamous epithelial tumour cells.