The proposed Kangir dam site is located in western Iran, Elam province, and will impound flow of the Kangir River. The foundation rocks comprise some limestones (Asamri Formation) and, to a greater extent, the marls, gypsum-bearing-marls, and gypsum strata of the Gachsaran Formation. To characterize the rock masses investigated at the dam site, rock mass classification systems such as rock mass rating, Q-tunneling index, rock quality designation, dam mass rating, geological strength index and rock mass index were all used. These classifications provide the basis for estimating deformation and strength properties, for supplying quantitative data to the design engineer, and they also present a platform for communication between exploration, design and construction groups. The results obtained from the comprehensive rock mass studies at the proposed dam site are presented and discussed in this article.