This volume presents an evaluation of the carcinogenicity of benzene, updating with new data the most recent evaluation provided in Volume 100F of the IARC Monographs. Benzene, a simple aromatic hydrocarbon, occurs naturally and as a result of human activity, notably as a result of combustion, and it is a high-volume chemical now used mostly as a chemical intermediate. Human exposure to benzene is widespread through the air, in consumer products, and in industry. An IARC Monographs Working Group reviewed epidemiological studies, animal cancer bioassays, and mechanistic data to assess the carcinogenicity of benzene and conducted quantitative analyses of data on genotoxicity and human cancer risks.