The tumor suppressor p16 is frequently inactivated in human cancer but poorly investigated in feline cancer. The feline p16 gene was cloned, and its polymorphism was characterized in domestic cats. Epigenetic regulation of the p16 was demonstrated in feline lymphoma cell lines. Genetic and epigenetic alterations of p16 were detected in feline cancer cell lines and primary cancers. Frequent promoter methylation of the p16 gene was observed in feline B-cell lymphoid malignancies.