Styrene-induced ototoxicity has been demonstrated in rats occurring after oral and inhalation exposure, and synergism has been noted with noise at subtoxic levels. While exposure thresholds for oral and inhalation routes have been established in animals, the lack of high-quality epidemiological studies has made it difficult to identify threshold levels of styrene in humans. The purpose of this systematic review is to identify the animal studies and critically appraise the epidemiological studies on the potential ototoxicity of styrene, with or without noise.