Two experiments were conducted with young chicks to study the effects of amino acid supplementation of diets containing autoclaved forms of the jack bean (AJB, Canavalia ensiformis). Beans were soaked in tap water for 24 h at 40°C and autoclaved for 5 min at 135°C in Experiment 1, and for 60 min at 121°C in Experiment 2. Basal diets containing 140 g AJB kg-1 were employed in both studies. Although brief autoclaving of beans permitted survival of all chicks, more prolonged autoclaving improved growth performance and efficiencies of food and N utilization. Irrespective of autoclaving treatments, chicks fed the AJB basal diet grew at slower rates, consumed less dry matter (DM) and utilized food less efficiently than control birds. In Experiment 1, arginine or arginine+ lysine additions to the AJB basal diet were equally effective in improving growth rates and DM intakes. Serum canavanine concentrations were unaffected by amino acid supplementation of the AJB basal diet. Urea-N excretion as a proportion of total N excretion was higher in chicks fed the AJB basal diet or AJB basal+ arginine than in those fed the control diet. In Experiment 2, supplements of ornithine, glycine, arginine and lysine, in different combinations, failed to improve growth rates, DM intakes or efficiencies of food and N utilization of chicks fed the AJB basal diet. In both experiments, AJB diets supplemented with amino acids failed to elicit growth performance and utilization of food to levels observed with the respective control diets.