To elucidate a role of TTV infection in patients with acute liver injury, TTV-DNA in the sera from 97 patients with acute liver injury of various etiology were determined according to Okamoto's method. Out of 77 patients with acute liver injury of determined etiology, 31 patients(40.3%) showed TTV-DNA positive, and out of 15 patients with acute liver injury of undetermined etiology, 8 patients(53.3%) showed TTV-DNA positive. These results suggested no evident role of TTV in patients with acute liver injury was shown. Further study including genotype and quantitative determination of TTV-DNA and antibody assay is needed.