An organotypic, tridimensional cell culture, also called a raft system, was used to study the influence of fibroblasts on epithelial carcinogenesis in a cell line derived from laryngeal squamous cell carcinoma and harboring a mutated p53. Differences between the effects of normal fibroblasts and those of tumor-derived fibroblasts were compared by means of fibroblasts taken from the normal skin and from the tumor of a cancer patient and cultivated with epithelial carcinoma cells in an organotypic culture. To study cell contact-mediated changes, the fibroblasts were either simply embedded in collagen matrix or additionally brought into direct contact with epithelial cells. Control epithelial cells were cultivated without any fibroblasts in an organotypic model. A protein panel [p53, p21, PCNA, bcl-2, Ki67, total cytokeratin (CK), CK 8, CK 10, CK 17, CK 18, CK 19, vimentin] involved in cell cycling and epithelial differentiation was assessed immunocytochemically in all organotypic cultures with fibroblasts, in tumor cells cultivated as a monolayer, and in the original tumor sample. The most dysplastic phenotype was obtained when tumor-derived fibroblasts were used in direct contact with epithelial cells, whereas the most benign phenotype was seen when skin fibroblasts had no contact with them. The intensive staining seen for p53 can be explained by p53 mutations also reflecting the weak expression of p21 and abundant expression of PCNA. The intensive Ki67 staining seen in all sections paralleled that of PCNA and marked active cellular proliferation. The CK staining pattern seen in cultured epithelia toward embryonic CKs, CK 8 and CK 18, suggested a simple epithelial phenotype. CK 19 was found only in the epithelium where no direct contacts had occurred. Vimentin expression increased when the raft epithelium was shifting toward a more benign phenotype. The results stress the importance of the origin of fibroblasts as well as the role of direct cellular contacts in modifying the epithelial phenotype even when the epithelial cells are malignant.