An overview is given on the effects of food processing on the protein digestibility. Beneficial effects of food processing are primarily observed in a range of plant foods containing toxic substances and/or anti-nutrients (legumes, cereals, some seed food). Digestibilities improve by heating, soaking, germination and fermentation. These processing steps reduce the amount of active enzyme inhibitors through extraction, inactivation by heat or microorganisms, or by compositional modification through germination. Reduced protein digestibility is primarily associated with excessive heat, exemplified by the comparatively low digestibility of ready-to-eat breakfast cereals. Experiments with model systems indicate that some caution should be observed with the use of alkalis in food processing, and with products prone to the Maillard reaction.