A survey of the baking behavior of commercially available soybean products was carried out to estimate their effects on dough properties by using farinograph. The parameters read on the farinogram are classified into two groups by the principal component analysis; one is concerned with dough stability and the other with water absorption. It was found that the addition of soybean products at level of 5% to wheat flour, in general, make the characteristics of flour stronger, i.e., increasing both stability and water absorption. The dough stability correlates positively with the amount of native protein of soybean product and, consequently, some native defatted soy flours perform the effective functions in this respect. The water absorption of dough has positive correlation both with the protein content and with the protein dispersibility of added soybean products, and negative correlation with the amount of native protein. The danatured but soluble soy protein isolate is, therefore, effective for increasing the water absorption of dough.