Malnutrition and growth retardation remain a major complication in infants with extrahepatic biliary atresia associated cholestasis. The purpose of this study was to investigate whether oral supplementation with branched chain amino acids (BCAA) can correct malnutrition in a rat model of biliary atresia. Four groups of 15 rats, 30 d old, were used. Group A were shamoperated animals, given a normal laboratory diet (17.5% of caloric intake as proteins). Group B were cholestatic rats (biliary atresia) fed a diet enriched in BCAA (supplement of 8.5%, valine/leucine/isoleucine ratio 1:1:1). Group C were cholestatic mice fed a diet enriched in casein (supplement of 8.5%). Group D were cholestatic mice fed a normal diet. Thirty-two days after surgery, groups were compared for body weight, serum amino acid content, nitrogen balance, muscle mass, and carcass composition. The results showed that the weight of group B, C, and D animals was 85, 81, and 64% of group A (controls). Serum BCAA levels were markedly increased in group B animals. Nitrogen retention was similar in groups B and A, but reduced to 63 and 44% in groups C and D, respectively. Dry weights were similar in group A (39.1% of body weight) and B (37.7%), but reduced to 28.1 and 28.6% of body weight in groups C and D. Body proteins were higher in groups A (13.9%) and B (14.2%) than in group D (9.7%) rats. Mineral content of group B animals was 84% of those of group A, 50% in group C, and 23% in group D rats. It was concluded that an oral supplement of BCAA can correct growth, nitrogen retention, and body composition in experimental biliary atresia. Administration of BCAA supplements to cholestatic infants should be considered.