Benzene derivatives can induce severe liver cell necrosis in animals. A case of a 40-year-old man whose daily consumption of alcohol was 200 g and who had a severe monochlorobenzene-induced liver necrosis is described. Liver biopsy specimen showed centrilobular and mediolobular necrosis, similar to that in mice after experimental bromobenzene administration. Monochlorobenzene serum concentration, assayed from day 3 to day 15 after poisoning, decreased monoexponentially with a half-life of 40.3 hours. Prostaglandin E1 was administered from day 3 to day 8. The patient ultimately recovered. The mechanism of monochlorobenzene-induced liver injury and the possible aggravating role of chronic alcohol consumption are discussed.