S-ALT (S-GPT) is to be measured weekly or biweekly after blood transfusion.1. Posttransfusion non-A non-B hepatitis is suspected in cases in whom S-ALT has increased after one week of blood transfusion to at least two times the normal upper limit at each laboratory twice or more successively.2. The diagnosis of non-A non-B hepatitis is established in cases in whom the increase of S-ALT to at least two times the normal upper limit has continued for at least three weeks with the S-ALT value elevating more than five times the normal upper limit at least once during the time.3. The above standards are not applied to cases showing S-ALT increase due to underlying diseases, postoperative liver dysfunction due to operation itself, liver damage due to drugs, fatty liver, hepatitis B, or other known viral diseases which manifest hepatitis symptoms.(Comment 1) To diagnose precisely, all patients receiving blood transfusion should be followed up weekly or biweekly after blood transfusion during for at least three consecutive months or longer, if possible.(Comment 2) For statistical studies patients with liver damage before operation are to be excluded.Liaison Council of Hepatitis Research GroupsThe Intractable Disease (Hepatitis) Research Committee Section for non-A non-B Hepatitis ResearchThe Research Committee concerning Posttransfusion Infection Section for Posttransfusion Hepatitis ResearchThis standards has been investigated and drawn up by the following members:H. Suzuki, K. Okochi, T. Miyagawa, S. Iino, K. Akahane, M. Shimizu, T. Takano, M. Yano, H. Tateda, Y. Egusa, A. Obayashi and T. Katayama