Clinical characteristics of transmitted transfusion virus (TTV) infection and its pathogenicity in children were evaluated. Serum TTV DNA from 118 children (mean age : 7.8±2 8 years) was detected by nested PCR. The product of PCR was cloned and sequenced. The positive rate for serum TTV DNA in 20 healthy children, 9 cases of acute hepatitis, 51 cases of chronic hepatitis, 24 cases of nephritis or nephrotic syndrome and 14 cases of hypoplastic anemia or acute leukemia was 20 %, 11 %, 29 %, 42 % and 21 % respectively, but there was no significant difference in TTV DNA frequency among them ( P >0.05). Of the 16 patients receiving immunosuppressive agent for a long time, 7 (44 %) were positive for TTV DNA, and of the 17 cases not receiving immunosuppressive agent, 5 (29 %) were positive with the difference being not significant ( P >0.05). Essential characteristics were pathogen carrier or asymtomatic infection in children with TTV infection. Long term employment of immunosuppressive agent did not increase the incidence in TTV infection. There was still high prevalence in TTV infection in healthy children not receiving blood product, suggesting the possibility of non hematogenous transmitted transfusion in TTV transmission. Clinical characteristics of transmitted transfusion virus (TTV) infection and its pathogenicity in children were evaluated. Serum TTV DNA from 118 children (mean age: 7.8 ± 2 8 years) was detected by nested PCR. The product of PCR was cloned and sequenced. positive rate for serum TTV DNA in 20 healthy children, 9 cases of acute hepatitis, 51 cases of chronic hepatitis, 24 cases of nephritis or nephrotic syndrome and 14 cases of hypoplastic anemia or acute leukemia was 20%, 11%, 29%, 42 % and 21% respectively, but there was no significant difference in TTV DNA frequency among them (P> 0.05). Of the 16 patients receiving immunosuppressive agent for a long time, 7 (44%) were positive for TTV DNA, and of the 17 cases not receiving immunosuppressive agent, 5 (29%) were positive with the difference being not significant (P> 0.05). Essential characteristics were pathogen carrier or asymtomatic infection in children with TTV infection. Long term employment of immunosuppre ssive agent did not increase the incidence in TTV infection. There was still high prevalence of TTV infection in healthy children not receiving blood product, suggesting the possibility of non hematogenous transmitted transfusion in TTV transmission.