Hepatic-Aid is purported to ameliorate encephalopathy and promote positive nitrogen balance in protein-intolerant, cirrhotic patients by correcting their imbalanced amino acid profile. This study evaluated Hepatic-Acid by comparing a 50-g Casein diet with an identical diet with 20-g Casein/30-g Hepatic-Aid per day in a cross-over study. Four patients with biopsy-proven stable cirrhosis, encephalopathy, and under-nutrition were studied. Each study period included three days of equilibration and eight days of metabolic balance, with the following measured at baseline and on balance days 5 and 8: routine biochemistry, fasting ammonia, psychometric tests, EEG, and plasma amino acid profiles. There was no significant change in clinical status, routine biochemistry, fasting ammonia, psychometrics or EEG between the two study periods. Mean (+/-SD) nitrogen balance on the Casein diet at 1.5 +/- 1.5 g/day was not significantly different from that on the Hepatic-Aid diet at 1.5 +/- 1.2 g/day. Plasma amino acid profiles showed a significant fall (p less than 0.05) in fasting and intraprandial tyrosine (tyr) and phenylalanine (phe) on Hepatic-Aid, but only intraprandial leucine (leu), isoleucine (ile), and valine (val) were significantly increased (p less than 0.05) on Hepatic-Aid. The ratio leu + ile + val to tyr + phe was significantly increased (p less than 0.05) on Hepatic-Aid. It is concluded that Hepatic-Aid, as given in this study, maintains N balance similar to Casein, alters the amino acid profile towards normal, but does not ameliorate encephalopathy.