Pleomorphic adenoma is the most frequently occurring benign neoplasm of the salivary glands. We describe the culture characteristics, biochemical properties, immunohistochemical staining, and genetic rearrangements found in a novel cell strain (UNC4) established from a human benign pleomorphic adenoma. Serum and/or butyrate stimulation of UNC4 cultures results in upregulation of mucin production. This is confirmed by periodic acid-Schiff, periodic acid-Schiff digest, alcian blue, and mucicarmine staining as well as by gel electrophoresis. Fluorescent immunohistochemical studies detect cellular cytokeratin, desmin, and epithelial membrane antigen. Immunofluorescent staining for S100 protein is negative. Examination of the karyotype of UNC4 reveals a unique rearrangement between one chromosome 8 and the two chromosome 9s involving the 8q12 locus. UNC4 represents an in vitro model of a benign salivary gland neoplasm that can provide the basis for further molecular and biochemical studies on genetic rearrangement and salivary mucin production.