Addition of 2% high molecular weight rye water-soluble pentosans to European bread wheat flour greatly changed its rheological and functional breadmaking properties. When the rye fractions were added as dry powder, the changes in the mixograph curves were smaller than the changes of the fractions that were presoaked in water and then added. Under the latter conditions, the mixograph peak height and area under the curve were greatly increased. Response surface methodology showed that the loaf volume of breads obtained from wheat flour is strongly dependent on mixing time and water addition. The addition of the rye components as a fine powder to wheat flour increased the water-absorption level and the range of mixing times for obtaining a bread of constant loaf volume and crumb quality. At the same time, it was possible to incorporate more water and to mix for a longer time without impairing the dough-handling properties. In general, the loaf volume increased and the crumb structure was comparable to that of the control. When the high molecular weight water solubles from rye were presoaked and added as a solution, the range of mixing times and the water-absorption level again were increased. Mixing time and water-absorption level strongly influenced loaf volume. The rye components used in this study, therefore, obviously influenced the quality of the wheat flour.