In this chapter, we summarize the evidence about known and suspected occupational carcinogens and cancer risk in humans. We list the agents of mixture for which, according to the definitions from the International Agency for Research on Cancer (IARC), there is sufficient evidence for carcinogenicity in humans (Group 1), and the agents (mixture) that are probably carcinogenic to humans (Group 2 A). We also summarize the estimates of the burden of cancer attributable to occupation for mesothelioma, lung, bladder, sinonasal, and laryngeal cancers. Finally, we comment on possible preventive strategies to avoid cancers caused by occupational exposures.