Bread dough was subjected to a high-voltage electric field (HVEF) during the first fermentation, and the bread firmness and the crystallinity of the starch (intensity of diffraction peak at 17.08° 2θ assigned to 4a; 5.24 Å d-spacing) isolated from the breads, which had been stored at 4 and 20°C, were examined. The HVEF treatment had the effects of reducing the bread firming at both storage temperatures as compared to the untreated bread. In this study, unexpected results were obtained for the crystallinity in the HVEF treated bread starches: while the firmness of the treated bread increased considerably after the first 3 days of storage at both temperatures, the rate of development in crystallinity was retarded at 20°C as compared with that of the untreated bread, but the opposite effect was observed at 4°C; that is, storing the bread at 4°C, the treated bread starch increased in crystallinity. These findings strongly suggest that crumb firming of the bread is involved in its water retention ability, taking into account the fact that the HVEF treatment made it possible to maintain bread softness longer than was possible for untreated bread. We, therefore, concluded that the increase in bread firmness was not closely related to the crystallinity of the bread starch, but was more influenced by the storage temperature.