International research on the possible health hazards in the use of benzotriazole is briefly reported. (See also Oddy, W.A., On the toxicity of benzotriazole , Studies in Conservation, 17, No. 3, p. 135 (1972).) The toxicity is uncertain but it is recommended that the use of precautions continue. Long-term testing is in progress by the National Cancer Institute in the U.S.A.