The aim of this study was to determine the prevalence of GB virus C (GBV-C) infection in pediatric patients receiving multiple blood transfusions in Turkey where HBV and HCV infections are common. Sera of a total of 148 children, of whom 85 had cancer and 63 hemoglobinopathies, were tested for GBV-C RNA and HCV RNA by RT-PCR and for antibodies to HBV and HCV. Demographic and clinical information as well as laboratory results were recorded for the patients (81 boys, 67 girls, aged 1-19 years). HBsAg positivity was found in 23 (15.5%) patients, HBV DNA positivity in 12 (8.1%), HCV RNA positivity in 9 (6.7%), and GBV-C RNA positivity in 4 (2.7%). There was no significant difference in the GBV-C RNA positivity between patients with cancer (3.2%) and patients with hemoglobinopathies (2.4%) (p > 0.05). GBV-C RNA was found in 4 (3.1%) out of 127 patients who had received transfusions, but it was not found in any of 21 patients who had not received transfusions. However, there was no relationship between GBV-C RNA positivity and the number of transfusions. Two of the patients with GBV-C RNA had high levels of ALT (ALT > 40 IU). In these two patients, neither HBV DNA nor HCV RNA were detected by PCR, and serological tests were also negative for these agents. We concluded that pediatric patients who had multiple transfusions in Turkey are at risk of being infected with GBV-C, in addition to HBV and HCV. Investigation of GBV-C RNA in patients with high ALT levels in the absence of other viral markers may be useful.