This paper examines the relationship between the mechanical properties of collagen samples and the stress and elongation behavior of this material due to changes in environmental relative humidity. The mechanical properties are determined by both rapid and equilibrium stress-strain testing at fixed environments whereas free swelling and restrained sample desiccation were used to examine changes in length and stress as a function of relative humididty. The data developed show that the changes in moisture can produce stress magnitudes in collagen nearly identical to those determined by the equilibrium stress-strain test.