This study evaluates the effects of storage and water activity (aw) on the chemical and nutritional composition of cocoyam, soybean flours and their various blends. Reports on effects of water activity (aw) which can be used to evaluate the nutritional quality of these products are at best, scanty, and in some case, apparently non-existence. The method used involved preparing three saturated solutions that gave water activities of 0.11(LiCl), 0.33(MgCl2), and 0.75 (NaCl), respectively. The Colocasia exculenta and Glycine max samples were thus stored under the various water activities for 3-months and changes in the nutritional and chemical quality indices were monitored during the 3-months storage using the AOAC (2004) methods. Significant changes occurs in the chemical constituents of Colocasia exculenta and Glycine max flours (including their blends) which are traceable to factors such as aw, blending proportions, length of storage. Important chemical changes occurred during the 3-month storage.