This investigation statistically examines the strength development on alkaline activation of metakaolin (Mk)/blast furnace slag (BFS) pastes. The main parameters studied are: BFS/Mk weight ratio (100/0, 80/20, 50/50, 20/80, and 0/100), modulus of the alkaline solutions of sodium silicate (M=SiO2/NaO2 at 0, 1, 1.5, 2), %Na2O (5%, 10%, and 15%), and curing time. Cubes were cured at 20 degrees C for up to 360 days; the compressive strength and other characteristics were investigated. A fully factorial experimental design was used to determine the influence of each variable. The curing time and the interaction of the factors BFS/Mk ratio-%Na2O were the most important, followed by the modulus and then the %Na2O; others such as the interaction BFS/Mk ratio modulus were less important. The results indicated that the addition of Mk to BFS reduced the strength, more notably at contents above 50%. For strength development, the most effective modulus was Ms=1 and higher %Na2O were required with higher Mk loads.