Background: Diabetes Mellitus (DM) comprises a group of common metabolic disorders that share the phenotype of hyperglycemia. Increasing age, family history, race, obesity, hypertension, and history of vascular disease are known predisposing factors for diabetes. It seems that chronic hepatitis C and HIV/HCV co-infection and antiretroviral treatment (ART) especially regimen contains protease inhibitors may predispose to diabetes. Regard to more prevalence of diabetes in HCV infected patients in other studies and also increasing number of HIV infected cases and HIV infected patients treating with antiretroviral drugs in the country and importance of early diagnosis and control of chronic disease in these patients, this study was conducted to determine prevalence of diabetes in patients with HIV and HCV infection.Methods: In this descriptive cross-sectional study, the registries of 150 HCV patients and 50 HIV patients and 90 HIV/HCV co-infected patients in hepatic clinics and consulting center for behavioral disorders of Kermanshah University of Medical Science in 2007 which selected by convenience sampling, were studied. Data of age, sex, duration of disease, history of injection drug user (IDU), liver enzymes level, CD4 count, ART, treatment with interferon (IFN), and blood sugar level were collected. If they had two fast blood sugar (FBS) ≥126 or random blood sugar (BS) ≥200 were described diabetic. The data analyzed by SPSS software with chi-square, Fisher and Z tests Results: The prevalence of diabetes was 2.7% among patients infected with HCV, and 4% in patients infected with HIV and 2.2% in patients co-infected with HIV/HCV. None of the variables including age, sex, liver enzyme, injecting drug usage, CD4 count, antiretroviral treatment, and interferon were determined as risk factors for diabetes.Conclusion: Although we didn't find any significant correlation between HIV and HCV infection and HIV/HCV co-infection with increasing risk of diabetes, but according to previous studies and incomplete information about some diabetes risk factors in our registries such as BMI, staging of cirrhosis, HCV viral load and nutrional status of HIV infected cases and exclusion of subjects with only one abnormal FBS from our samples, we recommended regular measurement of FBS for HIV, HCV infected and HIV/HCV co-infected patients and designing supplement studies considering these risk factors.