The physical properties of mortars, the bond strength of the mortars to masonry units, and the structural strength of concrete masonry and composite masonry walls containing the mortars are discussed and compared. All of the mortars were tempered to as wet a consistency as could be conveniently handled by the mason. The compressive strength of the walls increased, in general, with the compressive strength of the mortar. The racking and flexural strengths of the walls increased with the bond strength of the mortar. The strength of bond test specimens tended to increase with the compressive strength of the wet consistency mortars that were used. However, bond strength appeared to be the dominant factor affecting the racking and flexural strength of the walls. Increase in both bond strength and wall strength with compressive strength of the mortar was not proportional to the relative compressive strengths of the type N and type S mortars. The stiffness of walls subjected to compressive and flexural loads increased with the bond and compressive strength of the mortars. However, the stiffness of walls subjected to flexural loads appeared to be more dependent upon the number of bed joints in the tensile face and on their extension in bond than upon the bending strains in the masonry materials.