The main transmission route of TT virus (Transfusion-Transmitted Virus, TTV) and hepatitis G virus (HGV) is by parenteral route of blood and blood-products. Since they form the same risk group, some of TTV or HGV positive patients may also be infected by hepatitis B virus (HBV) and/or hepatitis C virus (HCV). In this study, the presence of TTV and HGV has been investigated by reverse transcriptase-polymerase chain reaction (RT-PCR, GeneAmp 5700 Sequence Detection System, AB), in 40 hepatitis B, 30 hepatitis C and 5 hepatitis B and C co-infected patients, 50 HBV and HCV negative hemodialysis patients, and 50 randomly selected healthy blood donors. As a result, 37 (21.1%) TTV and 11 (6.3%) HGV positivity were detected, out of a total 175 cases. The positivity rates for TTV and HGV were found as 40% and 5% in HBV-positive, 23.3% and 20% in HCV-positive, 20% and 20% in HBV+HCV co-infected patients, 20% and 4% in hemodialysis patients, and 6% and 0% in healthy blood donors, respectively. In conclusion, as the positivity rates were not low for these viruses, their role on the hepatitis pathogenesis should be further investigated by detailed studies.