This study was aimed at the evaluation of cell proliferation, p53 level and apoptotic index by immunohistochemical methods in canine oral papillomatosis. The study material comprised of tumor tissue samples taken from six dogs being admitted to the Pathology Department of Faculty of Veterinary Medicine, Kafkas University, Kars, Türkiye. Choice of immunohistochemical staining was avidin-biotin peroxidase method. Cases of canine oral papillomatosis, determined to have been caused by canine papillomavirus-1, were found to have a rather high cell proliferation index. Furthermore, all cases were immunohisto-chemically demonstrated to carry a mutant p53 gene. Despite the mutation of p53 gene, the shift in the Bax/Bcl-2 ratio of dogs diagnosed with tumor was in favor of the pro-apoptotic Bax gene. The apoptotic mechanism was determined to occur through both the caspase-dependent and caspase-independent pathways. While the lesions occupied the entire oral cavity in some cases, histopathologically, malignant transformation was not detected in any of the six cases.