Tumor incidence patterns over the course of 350 days in F1 hybrids between partially resistant C.D2-Fv1 and hypersusceptible C.D2-Idh1, Pep3 (C.D2-IP3) mice. Studies were terminated in the C.D2-IP3 mice at day 226 because of high morbidity and mortality in this strain. Resistance was semidominant in the F1 hybrids between Fv1 and IP3 mice.