The half-lifetime of polyacrylamide (PAM) in aquatic environments was evaluated by determining the bimolecular rate constants that govern the reaction of PAM and the hydroxyl radical (OH center dot) in aqueous solution. Rate constants of 1.5 x 10(9) and 2.0 x 10(9) M-unit(-1) s(-1) were determined at 293 K using a competitive kinetics technique at pH 4 and 8, respectively. Both constants showed little dependence on temperature between 10 and 40 degrees C.