Particle size distributions showed that flours with finer granulation produced breads with better crumb grain score. Breadmaking quality of flours fractionated by sieving was influenced more by differences in protein content rather than flour particle size. Reducing flour particle size by further pin-milling improved loaf volume up to 5%, but the results of crumb grain score were inconsistent. Gas cells in bread crumb became elongated with particle size reduction. Crumb grain score was correlated positively with flour protein content and some protein subclasses, but was more highly correlated with rheological mixing properties of dough. Most protein subclasses were correlated positively with loaf volume but negatively with mixograph mix time. On the other hand, insoluble (50% aqueous 1-propanol) polymeric protein showed a positive correlation with the mix time.