Odutola M, Jedy-Agba E, Oga E, Igbinoba F, Out T, Ezeome E, Ekanem I, Hassan R, Adebamowo C. Background Infections by certain viruses, bacteria, and parasites have been identified as risk factors for some cancers. We carried out this study to evaluate the numbers of cancers in Nigeria from 2012-2014 attributable to infections using data from Population Based Cancer Registries [PBCR] in Nigeria. Methods We considered cancers associated with Epstein-Barr virus [EBV], Human Papilloma Virus [HPV], Hepatitis B and C Virus [HBV/HCV], Human Immunodeficiency Virus and Human Herpes Virus 8 [HIV/HHV8], Helicobacter pylori and Schistosoma haematobium that have been classified as oncogenic by IARC. We obtained data on infection associated cancers from the registry databases of 3 PBCR in Nigeria; Abuja, Enugu and Calabar cancer registries. We used Population Attributable Fraction for infectious agents associated cancers in developing countries that were calculated using prevalence data and relative risk estimates in previous studies. Results The 3 PBCR reported 4861 cancer cases from 2012-2014; 1875 in males and 2986 in females. There were 412 infection-associated cancers in males accounting for 22% of total cancers in males, and 351 (85%) of these were attributed to infections. In female, there were 727 infection-associated cancers accounting for 24% of all cancers in females and of these, 674 (93%) were attributable to infections. Cancers of the Cervix (n = 430) and Liver (n = 152) as well as Non-Hodgkin’s Lymphoma (n = 129) were the commonest infection-associated cancers in both sexes. The commonest infectious agents associated with cancers were HPV (n = 453), HIV/HHV8 (n = 199), HBV/HCV (n = 143) and EBV (n = 125). Conclusion Our finding suggests that 85% of infection-associated cancers in males and 93% infection-associated cancers in females can be prevented with vaccination, safer risk behaviours or anti-infective treatments.