A novel DNA sequence belonging to a new genotype of TT virus (TTV) was detected by long-distance PCR in the serum of a chronically HCV-infected patient. The isolate was designated KAV according to the patient's initials. Extending the sequence to full length revealed a 3705-nt viral genome, which is about 100 nucleotides shorter than the other TT-viruses. KAV showed common features with the TTV family, such as the organization of open reading frames and conserved noncoding regions. The largest open reading frame of KAV (ORF 1) was about 40 aa shorter than that of other TT-viruses. Overall sequence homology with known TTV isolates was less than 66%. Phylogenetic analysis poses KAV in one major group with three recently published TTV sequences. So KAV can be considered as a new genotype of the TTV family (provisionally designated genotype 28).