The magnitude of HIV/AIDS in Ethiopia is ever increasing. It is also believed that the use ofrnsubstances is increasing in some major towns including Addis Ababa. However, data regardingrnthe relation of substance abuse and HIV infection is lacking.rnA case-control study was carried out in Addis Ababa from December 2001 to February 2002 tornexplore the association between substance abuse and HIV infection and to determine thernprevalence and the factors related to substance abuse among people visiting HIV testing andrncounseling centers.rnAmong all visitors for HIV testing and counseling, 227 cases and 726 controls were identified.rnCases and controls were compared by socio demographic, socio economic, exposure tornsubstances and risky behaviors that predispose them to HIV infection.rnThe prevalence of â€œhardâ€™ drug use was found to be 1.2% with the rate being 3.2% in the casesrnand 0.54% in the controls. Alcohol drinking was found to be associated with serum HIVrnpositivity after controlling for other confounding variables. While young age of 15 to 24 andrnbeing single were found to be associated with serum HIV positivity, having monthly familyrnincome was found to be protective against HIV infection. Being male and having sex withrncommercial sex workers were related to both alcohol drinking and khat chewing.rnFrom the study, we concluded high prevalence of alcohol and khat abuse among people visitingrnHIV counseling and testing centers. Alcohol was found to be a significant risk factor for HIVrninfection among people visiting HIV testing and counseling centers. The need of healthrneducation to bring behavioral changes and further study to identify the prevalence and role ofrnsubstance in exposure to HIV infection in the community is recommended.