The effect of PG on patients with fulminant and subfulminant viral hepatitis (FHF) was studied. 17 patients presented with FHF secondary to hepatitis A (n = 3), hepatitis B (n = 6), and non-A, non-B (NANB) hepatitis (n = 8). 14 of the 17 patients had stage III or IV hepatic encephalopathy (HE). At presentation the mean aspartate transaminase (AST) was 1,844 +/- 1,246 U/liter, bilirubin 232 +/- 135 mumol/liter, prothrombin time (PT) 34 +/- 18, partial thromboplastin time (PTT) 73 +/- 26 s, and coagulation Factors V and VII 8 +/- 4 and 9 +/- 5%, respectively. Intravenous PGE1 was initiated 24-48 h later after a rise in AST (2,195 +/- 1,810), bilirubin (341 +/- 148), PT (36 +/- 15), and PTT (75 +/- 18). 12 of 17 responded rapidly with a decrease in AST from 1,540 +/- 833 to 188 +/- 324 U/liter. Improvement in hepatic synthetic function was indicated by a decrease in PT from 27 +/- 7 to 12 +/- 1 s and PTT from 61 +/- 10 to 31 +/- 2 s, and an increase in Factor V from 9 +/- 4 to 69 +/- 18% and Factor VII from 11 +/- 5 to 71 +/- 20%. Five responders with NANB hepatitis relapsed upon discontinuation of therapy, with recurrence of HE and increases in AST and PT, and improvement was observed upon retreatment. After 4 wk of intravenous therapy oral PGE2 was substituted. Two patients with NANB hepatitis recovered completely and remained in remission 6 and 12 mo after cessation of therapy. Two additional patients continued in remission after 2 and 6 mo of PGE2. No relapses were seen in the patients with hepatitis A virus and hepatitis B virus infection. Liver biopsies in all 12 surviving patients returned to normal. In the five nonresponders an improvement in hepatic function was indicated by a fall in AST (3,767 +/- 2,611 to 2,142 +/- 2,040 U/liter), PT (52 +/- 25 to 33 +/- 18 s), and PTT (103 +/- 29 to 77 +/- 44 s), but all deteriorated and died of cerebral edema (n = 3) or underwent liver transplantation (n = 2). These results suggest efficacy of PGE for FHF, and further investigation is warranted.