The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated benzotriazole [95‐14‐7], considering all toxicological endpoints. Available publications and unpublished study reports are described in detail. A genotoxic potential is not found in bacterial or mammalian cell systems in vitro and benzotriazole does not induce micronuclei in the bone marrow of mice. In oral carcinogenicity studies in rats and mice, benzotriazole causes tumours in various organs with a low incidence of glioma and oligodendroglioma in the brain of rats. These rarely occur in control animals and are therefore considered to be substance‐induced. For this reason, benzotriazole is suspected of being carcinogenic and is classified in Carcinogen Category 3B. A NOAEL of 12.5 mg/kg body weight and day is obtained for bleeding of mucous membranes at nose and mouth and salivation at 5 mg/kg body weight and day from a subchronic oral toxicity study in rats. As an inhalation study has not been performed, but benzotriazole is irritating to the eye and is therefore expected to be irritating to the respiratory tract, a maximum concentration at the workplace (MAK value) cannot be derived. In a reproductive toxicity study with exposure of rats to benzotriazole, at 300 mg/kg body weight and day the body weight of pups is reduced during lactation. Teratogenicity was not examined. Skin contact is expected to contribute significantly to systemic toxicity. Therefore, benzotriazole is designated with an “H”. Limited data show no sensitization.