Generally, a cured adhesive will absorb moisture from the ambient environment until it is in equilibrium with the environment at that temperature. When subjected to additional stress, it will absorb further moisture and establish a new equilibrium. Consequently, the long-term durability of any adhesively bonded joint is limited by the response of the adhesive to environmental factors, primarily moisture. Indeed, the combined environmental strains of temperature expansion and moisture swelling can exceed the elastic limit strain of an adhesive with low temperature and moisture resistance. These strains are further compounded by the effect of sustained (creep) loading. Under an Army program, we have evaluated the environmental and mechanical responses of several adhesive specimens concurrently by straining the specimens to failure at predetermined strain increments in an environmentally controlled chember. The adhesives stress-relax under the quasi-fixed displacements. Correlation is excellent between the equilibrium stress-strain behavior of the adhesives and their strengths and, more important, their joint performance. The mechanism(s) of stress-relaxation are discussed.