This paper aims to investigate the six heavy metal levels (Cd, Cr, Cu. Pb, Ni and Zn) in municipal solid waste (MSW) at different pHs. It intends to provide the baseline information of metals solubility in MSW co-disposed or co-digested with MSW incinerator ashes in landfill or anaerobic bioreactors or heavy metals contaminated in anaerobic digesters. One milliliter (equal to 1 mg) of each metal was added to the 100 ml MSW and the batch reactor test was carried out. The results showed that higher HNO3 and NaOH were consumed at extreme pH of 1 and 13 compared to those from pH 2 to 11 due to the comparably higher buffer capacity. Pb was found to have the least soluble level, highest metal adsorption (%) and highest partitioning K-d (l g(-1)) between pH 3 and 12. In contrast, Ni showed the highest soluble level, lowest metal adsorption (%) and lowest Kd (l g-1) between pH 4 and 12. Except Ni and Cr, other four metals seemed to show the amphibious properties as comparative higher solubility was found in the acidic and basic conditions. (C) 2008 Elsevier B.V. All rights reserved.