This work experimentally determined the effect of microwave treatment on the disintegration and acido-genesis of municipal secondary sludge. Sludge samples (500 g) were heated for 0, 3, 5,7, 9, 11, and 15 min in a microwave oven (2450 MHz, 700W). The solubilization degree (soluble chemical oxygen demand (SCOD)/COD) of sludge increased asymptotically with microwave irradiation time from 2% at 0 min to 22% at 15 min. The concentrations of soluble protein, carbohydrate, lipid, and calcium also increased with microwave irradiation time. The biochemical acidogenic potentials (BAP) of sludge increased from 3.58 to 4.77 g COD 1(-1). The results show that microwave irradiation increases the solubilization degree and BAP of municipal secondary sludge. (C) 2009 Elsevier B.V. All rights reserved.