This paper shows that the strength of an adhesive tested in bulk correlates well with its cohesive strength in a bonded joint if moisture equilibrium has been established, making it possible to predict the cohesive strength of a bonded joint from the equilibrium strength of the bulk adhesive. Previous investigators failed to arrive at this conclusion because they did not allow sufficient time for the moisture content in the adhesive to equilibrate with the RH of the environment. The findings from the present study opens the door to a more general design approach in which the tensile properties of polymeric materials can be used – along with those of steel, concrete, and various fiber materials – to predict the strength of composite members.