We studied the tissue plasminogen activator (t-PA) levels in the plasma of patients with acute hepatitis (AH), severe acute hepatitis (AHs) and fulminant hepatitis (FH). Plasma t-PA levels were measured consecutively on the first, third and seventh days of hospitalization. Plasma t-PA levels were markedly higher in AHs and FH than in AH (p < 0.05, p < 0.01, respectively) on the first day, but did not differ significantly between AHs and FH on this day. The t-PA levels decreased markedly on the third and seventh days in AHs (both p < 0.05), but did not change from the first day to the third and seventh days in FH. The t-PA levels on the third and seventh days were higher in FH than in AHs (both p < 0.05). There was a significant increase in the plasma t-PA level before an episode of encephalopathy in FH compared with levels in AHs. These observations suggest that t-PA level may be useful as a prognostic parameter in patients with acute hepatic injury.