Sprouting of red kidney beans resulted in a marked increase in the digestibility coefficient of both raw, 29.5% increased to 66.4%, and cooked beans, 69.3% increased to 84.4%. Sprouting also resulted in reduction of trypsin inhibitor activity by approximately 50%. The trypsin inhibitor from red kidney bean was fairly heat stable, inhibited the action of chymotrypsin, papain and pepsin at higher concentrations. In was fractionated into two components yielding molecular weights of 8000 and 5200 daltons. The content of the globulin E protein fraction decreased by approximately one-third as a result of sprouting. The specific activity of trypsin inhibitor activity in the globulin fraction was lower after sprouting. The digestibility coefficient of the globulin fraction, 62.5%, with its high trypsin inhibitor content was much higher than the whole beans 29.5%. The globulin fraction from bean sprouts had somewhat improved digestibility (73.4%), compared to the globulins from intact beans. It is concluded that the beneficial effects of sprouting on protein digestibility can not be attributed totally to a decline in trypsin inhibitor activity although it would appear to be a contributing factor.