Various test data on long-term (several to over 100 years of age) properties of dam concrete used for Japanese concrete dams were investigated and analyzed. The result indicates that the long-term compressive strength excesses early age strength in many cases, while it may be going to peak in some cases and the degree of strength increment may depend on bonding materials. In addition, test data of elastic modulus and tensile strength were analyzed in relation to compressive strength and material age. The rates of neutralization of dam concrete were also estimated and discussed.