The synthesis of polyurethane polymers in the presence of diisopropylfluorophosphatase (DFPase) has enabled the irreversible attachment of the enzyme to the polymeric matrix. The resulting bioplastic hydrolyzes diisopropylfluorophosphate (DFP) in buffered media up to 67% of the rate for the same amount of soluble enzyme. Above a DFPase concentration of approximately 0.1 mg/g(foam) the rate of the reaction catalyzed by the enzyme-containing polymer was controlled by internal mass transfer. Increasing foam hydrophilicity, via the use of nonionic surfactants during polymerization, significantly affected the structural properties of matrix, thereby enhancing the intrinsic and apparent efficiency of modified DFPase. The resulting reduction in internal mass transfer limitations was explained morphologically with electron microscopy.