One hundred forty four broiler cockerels, four-day old, were allocated to the four dietary treatments in a 4 x 2 factorial design experiment. The control diet was based on wheat while the four experimental diets contained four different varieties of rye and were supplemented either with xylanase or arabinofuranosidase or both enzymes together. Additionally, the dose effect of above enzymes on viscosity of water extract of rye was also examined. The obtained results showed, that xylanase plays an essential role in degradation of arabinoxylan polymers. All productive parameters were greatly enhanced when the diets were supplemented with xylanase preparation. The highest improvement was observed in body weight gain (37±4.5%) and the lowest in digestibility of dry matter (5±2.5%). In contrast to xylanase the effect of addition of arabinofuranosidase on improvement of growth performance of broiler chickens was distinctly less marked (from 9 to 0.4%). The effect of supplementation of rye diets with both enzymes was additive. The same tendency was observed in in vitro study. The greatest reduction in viscosity of water extract was obtained after incubation of water suspension of ground rye with xylanase and this effect was dose dependent. The viscosity of rye extract has been reduced by 67% in case of xylanase, by 45% in case of arabinofuranosidase and by 71 % in case of both enzymes added at the same concentration as in in vivo study. It seems, that fragmentation of the xylan backbone is decisive for utilization of rye by chickens.