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This work experimentally determined the effect of microwave treatment on the disintegration and acidogenesis of waste-activated sludges (WAS) from municipal and coke wastewater treatment plants. Sludge samples (500 g) were heated for 0, 3, 5, 7, 9, 11, and 15 min in a microwave oven (2,450 MHz, 700 W). The degree of sludge solubilization [soluble chemical oxygen demand (SCOD)/COD] increased asymptotically with microwave irradiation time from 1.5% at 0 min to 22.3% at 15 min for WAS from a municipal wastewater treatment plant (WASM) and 1.5% to 5.1% for WAS from a coke wastewater treatment plant of a steel manufacturing industry (WASC). The calcium concentrations in both sludges also increased with microwave irradiation time. The biochemical acidogenic potentials (BAP) increased from 3.70 to 4.44 g COD L-1 for WASM and 1.19 to 1.67 g COD L-1 for WASC. The results show that microwave irradiation increases the solubilization and BAP of sludges and that WASM had a higher degree of solubilization and BAP than WASC. [ABSTRACT FROM AUTHOR]