Swelling parameters were determined for 15 seed species; the swelling quotients were found to range from less than 1.1 (castorbean) to 2.8 (mungbean) and swelling coefficients ranged from 0.09 (castorbean) to 0.42 (cowpea). Swelling leads to a lowering of specific gravity of those seeds with high initial specific gravity, and an elevation of those with low initial specific gravity. The extent of swelling bears a linear relationship with moisture content. Redrying to air dryness only partially restores the original volume, but oven drying completely restores it. Temperatures alter both the rate and the extent of swelling. Solutes in the imbibing solution alter the dynamics of the volume increases, indicating several types of influences; these include osmotic effects, salt effects, valence effects, pH effects, and lyotropic effects. It is suggested that deformation resulting from imbibitional swelling may contribute to the stresses experienced by seed tissues during hydration.