Abstract: To study the liver histologic characteristics and the expression of Fas/FasL (Fas ligand) in liver tissuess of the patients with TTV (transfusion trsnsmitted virus) infection alone and to evaluate the possible pathogenetic role of apoptosis mediated by Fas/FasL system for the liver lesion in these patients.Eighteen cases of paraffin embedded liver tissues of the hospitalized patients with TTV infection occurred during an epidemic in a professional school in Wuhan city were observed by H&E stain, Gomori stain, and immunohematology stain.The histologic characteristics were as follow:portal tract inflammation 77.8% (14/18) , interlobular bile duct damage 33.4% (6/18) , focus necrosis 38.9% (7/18) , microvesicular fatty 16.7% (3/18) , and portal tract fibrosis 11.1% (2/18) .Out of Eighteen cases, Fas positive hepatocytes were detected in fourteen cases (77.8%) and more aggregated in periportal areas and necrosis areas.FasL positive hepatocytes were detected in eleven cases (66.1%) . FasL positive hepatocytes were esentially consistent both in expression degree and distribution pattern with Fas positive hepatocytes.TTV infection may be solely responsible for the liver mild inflammation of these patients, the characteristics of liver histology are portal inflammation and interlobular bile duct damage.Apoptosis mediated by Fas/FasL system may play an inportant role for the liver lesion in these patients.