Commercial samples of raw, dry-extruded, dry-toasted or wet-heated defatted soybeans had their centesimal composition determined and were investigated as feed for growing chicks with the aim of evaluating the effects of heating on their nutritional quality. None of the heat processes employed induced appreciable changes in the amino acid composition. Although dry-toasting reduced significantly the toxic and/or antinutritional proteins present in soybeans there was a trend toward a poorer nutritional performance of chicks fed on toasted soybeans. Dry-extrusion resulted in relative higher contents of bioactive proteins, particularly trypsin inhibitors, which although have not influenced negatively the performance of chicks caused pancreatic enlargement. The wet-heated defatted soybeans showed the highest nutritional quality. Thus, as a conclusion, the heat processing of choice must be one that promotes inactivation of the antinutritional and/or toxic proteins without destruction of essential nutrients. This study provides relevant data towards the establishment of adequate processing conditions for the production of soybean-based diets nutritionally effective for growing chicks.