The kinetics of the free‐radical‐catalyzed redox polymerization of aqueous acrolein have been examined. The reaction was found to be second‐order in acrolein, half‐order in instantaneous concentration of reducing agent, and independent of peroxide as long as sufficient amount was present. The reaction has a negative temperature coefficient, decreasing in rate as the temperature is raised. The redox system used was tert‐butyl hydroperoxide–polyacrolein hydroxysulfonic acid, and the rate of initiation was observed to vary directly with the pH and the temperature. Polymer molecular weight varied directly with acrolein concentration and indirectly with polyacrolein hydroxysulfonic acid concentration and the temperature. An empirical relationship may be represented as: [η] = K[M 0 ]/[C 0 ]1/4, where [η] is intrinsic viscosity (in deciliters per gram), [M 0 ] is the initial acrolein concentration, [C 0 ] is the initial reducing agent concentration; and K is a temperature‐dependent variable. The effect of trace impurities in acrolein on polyacrolein preparation was examined. Acetaldehyde and propionaldehyde had a retarding effect on polymerization rate. The effect of these components in reducing the molecular weight of the product increased in the order: acetaldehyde, propionaldehyde, and acetone.