Presented in the paper are findings of a project that examined the effect of slag grade and cement source on the performance of concrete mixtures. Slag cement contents were 20, 40, and 60 percent of the total cementitious material content. Two grades of slag cement were examined (Gr. 100 and Gr. 120) along with two sources of Type I cement. Compressive strength, durability, and permeability were measured. The results showed that the cement source affected the early age strength of the mixtures. At 28 days of age, mixtures containing Gr. 120 slag cement had higher compressive strengths than mixtures containing Gr. 100 slag cement, but by 90 days of age, the trend reversed. As for the chloride ion penetrability, mixtures cast with Gr. 100 slag cement passed fewer coulombs at 28 and 90 days of age than similar mixtures containing Gr. 120 slag. Mixtures containing Gr. 120 slag had the greatest durability factors.