Acrylamide was graft polymerized onto the surface of a biodegradable semicrystalline polyester, poly(epsilon-caprolactone). Electron beam irradiation at a dose of 5 Mrad was used to generate initiating species in the polyester. The degradation in vitro at pH 7.4 and 37 degrees C in a phosphate buffer solution was studied for untreated, irradiated and acrylamide-grafted polymers. In the case of poly(epsilon-caprolactone), all materials showed similar behavior in terms of weight loss. No significant decrease in weight was observed up to 40 weeks, after which the loss of weight accelerated. The main differences in degradation behavior were found for the average molecular weights, (M) over bar(n), and M,. Virgin poly(epsilon-caprolactone) maintained M, and M, up to about 40 weeks, whereas the irradiated and grafted poly(epsilon-caprolactone) showed similar continuous declines in (M) over bar(n) and (M) over bar(w) throughout the degradation period.