Relative to wild-type littermates, p19 Arf−/− mice had an average of 2.97 more papillomas (95% CI (0.70, 5.24); p = 0.010) and p19 Arf+/− mice had an average of 2.60 more papillomas (95% CI (0.05, 5.14); p = 0.045) in weeks 18–30 after DMBA administration. The gene discussed is CDKN2A; the disease is papilloma.