Dimethyl carbonate (DMC) is a unique molecule having versatile chemical reactivity. In many aspects, DMC is an environmentally benign building block. DMC is a safe substitute for dimethyl sulfate or methyl halides. These conventional methylating agents are toxic and corrosive and give a stoichiometric amount of inorganic by-products. Methylation with DMC is often very selective. The mono-methylation of phenylacetonitrile, O-methylation of phenol and N-methylation of aniline are such examples. The transesterification of DMC with phenol yields methyl phenyl carbonate, which gives diphenyl carbonate by further transesterification with DMC or the disproportionation. Diphenyl carbonate is an essential starting material for polycarbonates resins by "non-phosgene" process. DMC serves also as a methoxycarbonylation agent. The methoxycarbonylation of amines with DMC gives methyl carbamates, which can be converted into isocyanates by decomposition. DMC reacts with silica at 550-600 K to afford tetramethoxysilane. This gas-solid reaction gives a simple and convenient method to depolymerize silica. In this review, various aspects of the reactions of DMC and the catalysts involved in the reactions will be overviewed.