The toxicity of melamine caught the attention of physicians as a result of a recent spate of renal injury after exposure to melamine-tainted milk in China. Melamine is an organic nitrogenous compound used in the production of plastics, dyes, fertilizers, and fabrics. In the current incident, melamine was added to milk to elevate falsely assay results for protein content. A variety of toxic effects from melamine, including nephrolithiasis, chronic kidney inflammation, and bladder carcinoma, all have been studied in animals. We review here the epidemiology, clinical features, and investigative findings concerning the only outbreak of melamine poisoning in humans. We also examine the renal toxicities of melamine and cyanuric acid--a by-product of its synthesis--and the associated risk factors on exposure and provide guidance on levels in foods.