The relation between donor alanine aminotransferase (ALT) and recipient post-transfusion hepatitis (PTH) non-A, non-B was studied in patients tested before and 6 and 12 weeks after transfusion. The minimum ALT criterion for PTH was 105 IU/l (>2.5 times the upper normal of 42 IU/1). In 8.8% of donors, ALT was >42 IU/l, and in 2.3% ALT was >63 IU/l, i.e., 1.5 times elevated. PTH non-A, non-B occurred in 14 of 742 recipients. The PTH incidence increased when donor ALT was above 63 IU/l (1.5 vs. 5.6%; p<0.05). However, if the confounding factor of volume variations was compensated for, elevated donor ALT and PTH were only statistically linked among recipients <70 years (p<0.02; Mantel-Haenszel test).