Background HIV/AIDS is the leading cause of death in Africa accounting for more than 20% of all deaths. Major concerns have been expressed regarding the continued rise of HIV infections among specific cultural groupings.

Objective To describe the association between socio-cultural practices (circumcision and pubic hair removal) and HIV infection risk in informal urban settlements.

Methods Data were collected from the Nairobi Urban Health and Demographic Surveillance System between January 2007 and December 2008. A total of 4767 residents of Viwandani and Korogocho slums, between the ages of 15–54 years for males and 15–49 years for females were recruited. Data were collected using interviewer-administered questionnaires. HIV serostatus was assessed using DetermineÒ HIV-1/HIV-2 (Abbott) and Uni-Gold Test kits.

Findings The highest HIV infection burden was observed among participants aged 25–34 years (40%). Among HIV+ men, 64% were circumcised compared to 88% among HIV− men. Majority of participants were circumcised before they were 12 years old and there were no differences among the HIV+ and the HIV−. A similar proportion of HIV+ (85%) and HIV− (83%) individuals had ever removed/shaved their pubic hair. After controlling for certain factors, circumcised men had a threefold reduced risk of developing HIV (OR 0.28; 95% CI 0.16 to 0.47; p<0.01) whereas those that had ever removed their pubic hair had only a onefold reduced risk of developing HIV (OR 0.98; 95% CI 0.48% to 1.98%; p>0.05).

Conclusion Our study found an association between circumcision and HIV, supporting findings from other studies.