There has been much effort recently to probe the long-recognized relationship between the pathological processes of infection, inflammation and cancer. For example, epidemiological studies have shown that∼ 15% of human deaths from cancer are associated with chronic viral or bacterial infections. This Review focuses on the molecular mechanisms that connect infection, inflammation and cancer, and it puts forward the hypothesis that activation of nuclear factor-κB (NF-κB) by the classical, IKK-β (inhibitor-of-NF-κB kinase-β)-dependent pathway is a crucial mediator of inflammation-induced tumour growth and progression, as well as an important modulator of tumour surveillance and rejection.