Process characteristics of nonliving free radical polymerization of acrylamide in capillary microreactors were investigated at high temperatures (70-90 degrees C). Poly(acrylamide) with M-n of 3.4 X 10(5) g.mol(-1) and polydispersity index of 2.6 could be obtained with 1.61 min residence time at 70 degrees C. The reaction mixture viscosity increased significantly during polymerization resulting in high pressure drops in microreactors. The reaction mixture changed from Newtonian fluid to non-Newtonian fluid with the polymerization processing. Furthermore, the rheological test indicated that hydrogels were produced in this polymerization process. Reynolds number and Bodenstein number were calculated to evaluate flow behaviors in microreactors. Low values of Re and Bo indicated strictly laminar flow and obvious deviations from plug flow in capillary microreactors during the polymerization. On the basis of pressure drop measurement, the energy balance calculation was conducted to assess the energy consumption during the polymerization. Moreover, the polymerization performance in the microreactor was compared with that in the batch reactor.