In 5 growth trials with a total of 420 pigs, tryptophan requirements from 20 to 40 kg liveweight were estimated. L-Tryptophan 0, 0.15, 0.30, 0.45 and 0.60 g/kg was added to a basal diet containing tapioca, barley and maize, with CP 162 g/kg and tryptophan 1.65 g/kg. The control diet was supplemented with lysine, methionine plus cystine, threonine, isoleucine, valine and histidine to assure that only tryptophan was limiting pig performance. Diets were freely given as pellets. Total tryptophan was about 2.10 g/kg for optimal weight gain and feed conversion efficiency in a diet containing NE 9.5 MJ/kg, corresponding with apparent ileally digestible tryptophan 1.77 g/kg.