We have developed an epithelial cell line derived from mouse liver which represents a spectrum of malignant progression. When inoculated into mice at low passage, the cells induced benign cysts; after extensive subcultures, the same line induced low grade adenocarcinomas. A variant of these cells with increased invasive and metastatic potential was selected. In culture, growth in methocel correlated with acquisition of malignant potential while increased homotypic aggregation correlated with metastatic ability. These cultures should be extremely valuable for studies on the nature of epithelial cell malignancy, the most common form of human cancer.