Electron spin resonance spectroscopy revealed that some free radicals were trapped in the precipitated polymer during the precipitation polymerization of acrylamide conducted in nonsolvents of the polymer [t-butyl alcohol (TBA), acetone and methanol]. The trapped radical concentration decreased with an increase in the chain-transfer activity of the aforementioned liquids. A 100% polymerized acrylamide in TBA prepared with a 10% monomer concentration and a 3 X 10(-3) mol/dm(3) azobisisobutyronitrile concentration at 50 degreesC contained approximately 2 radicals per 100 polymer molecules. The trapped radicals on exposure to air decayed with time according to second-order kinetics. The rate constant was evaluated and found to be in reasonably good agreement with the rate constant evaluated from data published long ago for the decay of trapped polyacrylonitrile radicals following their exposure to air. (C) 2003 Wiley Periodicals, Inc.