Total parenteral nutrition with branched chain amino-acids enriched solutions has been advocated in patients with sepsis and stress because of favourable effects on nitrogen balance, protein synthesis and immune competence. The rationale for the use of BCAA-enriched solutions is based on their potential to correct the plasma amino-acid imbalances seen in these patients. In a 7-day prospective randomised study we investigated the effects on plasma amino-acid concentrations of a standard amino-acid solution (15.6% BCAA) and a branched chain amino-acid enriched solution (50.2% BCAA) in 101 parenterally fed patients with carefully assessed sepsis and/or stress scores. The infusion of the BCAA-enriched solution led to an imbalance of the essential plasma amino-acids. The branched chain amino-acids valine, leucine and isoleucine increased significantly while the non-BCAA essential amino-acids decreased significantly. In the standard solution the non-BCAA-essential amino-acids increased significantly with a slow and insignificant rise in the levels of the branched chain amino-acids. We conclude that infusion of a BCAA enriched TPN formulation induced amino-acid profile derangements that can be considered ill-suited to the achievement of anti-catabolic effects.