Classical and molecular methodologies were used to determine the inheritance of Phytophthora root rot (PRR) resistance in red raspberry. The varieties 'Latham' and 'Titan,' resistant and susceptible, respectively, were used to create F1, F2, B1, B2, and S1 populations for analysis. Generational means analysis was used to calculate the components of genetic variation and estimates of narrow and broad sense heritability for the plant disease index and the incidence of petiole lesions. The plant disease index showed additive genetic variation with additional signiWcant interactions, but the incidence of petiole lesions was non-additive. A dominant, two-gene model was shown to be the best Wt for the observed segregation ratios when classiWcation for resistance was based on a combination of all criteria measured. Molecular linkage maps were generated from the segregating B2 population. Linkage maps of both parents were constructed from ampliWed fragment length polymorphism (AFLP), Random ampliWed polymorphic DNA (RAPD), and uncharacterized resistant gene analog polymorphism (RGAP) markers with seven linkage groups each totaling 440 and 370 cM of genetic distance, respectively. An analysis of the distributional extremes of the B2 population identiWed several RAPD markers clustered on two linkage groups associated with PRR resistance. QTL analysis identiWed two similar genomic regions on each map that explained signiWcant percentages of phenotypic variation observed for the disease assessment criteria. Genetic mapping supports the dominant two-gene model developed from generational means analysis. The results reconcile conXicting reports on inheritance of PRR resistance, provide a basis for further investigation of durable resistance to Phytophthora caused diseases, and indicates that recurrent selection is the appropriate approach for the development of newresistant cultivars.