A case-control study was carried out to assess the risk factors associated with hepatitis C in patients infected with human immunodeficiency virus. One hundred eighteen patients tested positive for hepatitis C virus (HCV) and were included as cases, and 117 tested negative for HCV and were included as controls. Information was collected through a questionnaire. The risk factors that showed a significant association with co-infection by multivariate analysis were an age of 30-39 years (odds ratio [OR] = 4.65, 95% confidence interval [CI] = 1.31-16.43), an age of 40-49 years (OR 6.48, 95% CI = 1.70-24.78), an age > 50 years (OR = 7.50, 95% CI = 1.54-36.68), use of intravenous drugs (OR = 25.46, 95% CI 4.91-131.88), use of inhaled illicit drugs (OR = 3.56, 95% CI 1.22-10.44), anal intercourse (OR 3.93, 95% CI = 1.27-12.13), a sexual partner with a history of liver disease (OR 5.45, 95% CI = 1.33-22.32), a sexual partner with a history of blood transfusions (OR = 4.79 95% CI = 0.95-24.19), and sexual partner with a history of intravenous drug use (OR = 3.46, 95% CI = 1.24-9.65).