Lincosamides are among the most frequently detected antibacterial agents in effluents from wastewater treatment plants and surface runoff at agricultural production systems. Little is known about their transformations in the environment. This study revealed that manganese oxide caused rapid and extensive decomposition of clindamycin and lincomycin in aqueous solution. The reactions occurred mainly at the pyranose ring of lincosamides, initially by formation of complexes with Mn and cleavage of the ether linkage, leading to the formation of a variety of degradation products via subsequent hydrolytic and oxidative reactions. The results of LC-MS/MS and FTIR analysis confirm cleavage of the C-O-C bond in the pyranose ring, formation of multiple carbonyl groups, and transformation of the methylthio moiety to sulfur oxide. The overall transformation was controlled by interactions of cationic species of lincosamides with MnO(2) surfaces. The presence of electrolytes (i.e., NaCl, CaCl(2), and MnCl(2)) and dissolved organic matter in aqueous solution, and increase of solution pH, diminished lincosamide binding to MnO(2) hence reducing the rate and magnitude of the transformations. Results from this study indicate that manganese dioxides in soils and sediments could contribute to the decomposition of lincosamide antibiotics released into the environment.