In February, 2009, 36 scientists from 16 countries met at the International Agency for Research on Cancer (IARC) to reassess the carcinogenicity of the biological agents classified as “carcinogenic to humans” (Group 1) and to identify additional tumour sites and mechanisms of carcinogenesis (tables 1 and 2). These assessments will be published as part B of Volume 100 of the IARC Monographs.1