Background: HEPATITIS G virus (HGV) is a hepatotrope virus with unknown importance. The genome of the virus has been detected in patients with acute or chronic non-A-E HEPATITIS, cirrhosis, and hepatocellular carcinoma. The aim of this study was to determine the association between HEPATITIS G and unknown chronic HEPATITIS.Methods: This case-control study was performed in Ebne-Sina military hospital in Hamadan, Iran. The cases were 35 military staff with unknown chronic HEPATITIS. The control group consisted of 59 healthy subjects who had normal levels of serum alanine aminoteransferase (ALT). The data were analyzed by SPSS, version18, using Fisher’s exact test, the Student’s t-test, and multivariate logistic regression analysis.Results: Only one patient in the case group (2.9%) tested positive for HGV antibodies, and no one was infected in the control group. There was no association between HGV infection and unknown chronic HEPATITIS in our study (P=0.37). A significant association was found between the male gender and unknown chronic HEPATITIS (OR=14.9, P=0.01).Conclusion: No association between HGV infection and unknown chronic HEPATITIS was found in our study, so it was not necessary to evaluate these patients for HGV infection.