The prevalence of hepatitis C virus (HCV) and a newly identified hepatitis G virus (HGV) and their clinical significance were studied in 42 polytransfused Taiwanese children. Serological assays for antibodies against HCV (anti-HCV) and polymerase chain reaction for serum HCV ribonucleic acid (RNA) and HGV RNA were performed. The prevalence of anti-HCV and HGV RNA was 17% and 14%, respectively in 42 polytransfused children. Anti-HCV seropositives had a significantly higher mean age, peak serum transaminase level, and longer transfusion duration than seronegatives, while children with HGV infection usually had no or only mild hepatitis activities. The prevalence of anti-HCV dropped sharply after implementation of anti-HCV screening, however the prevalence of HGV viraemia remained unchanged. CONCLUSIONS HGV infection is not uncommon in polytransfused Taiwanese children and the virus does not cause significant hepatitis compared to HCV infection. Current blood donor screening for anti-HCV can effectively protect polytransfused children from HCV infection but the impact of additional screening for HGV markers awaits further studies.