Epidemiological studies support a link between melanoma risk and UV exposure early in life, yet the molecular targets of UV's mutagenic actions are not known. By using well characterized murine models of melanoma, we provide genetic and molecular evidence that identifies components of the Rb pathway as the principal targets of UV mutagenesis in murine melanoma development. In a melanoma model driven by H-RAS activation and loss of p19(ARF) function, UV exposure resulted in a marked acceleration in melanoma genesis, with nearly half of these tumors harboring amplification of cyclin-dependent kinase (cdk) 6, whereas none of the melanomas arising in the absence of UV treatment possessed cdk6 amplification. Moreover, UV-induced melanomas showed a strict reciprocal relationship between cdk6 amplification and p16(INK4a) loss, which is consistent with the actions of UV along the Rb pathway. Most significantly, UV exposure had no impact on the kinetics of melanoma driven by H-RAS activation and p16(INK4a) deficiency. Together, these molecular and genetic data identify components of the Rb pathway as critical biological targets of UV-induced mutagenesis in the development of murine melanoma in vivo.