Normal colonies of bees given a supply of empty drone combs as required during the active season (Treated group) produced significantly more drone brood than Control colonies in which the amount of drone comb was severely restricted in the spring. A natural limit was fairly soon reached, however, and the maximum amount did not exceed about 2 580 sq. cm. in any colony. (In a previous year Treated colonies given only one drone comb also produced significantly more drone brood than Control colonies with no added drone comb.) Fewer drone cells were built on worker combs in the Treated colonies than in the Controls. Worker brood amounts and honey yields were not significantly less in Treated than in Control colonies, nor was there an increased tendency towards queen rearing in the Treated groups. Allowing colonies to rear drones freely would therefore appear to have no detrimental effect on their economic performance, and the need to restrict drone rearing as a beekeeping practice may be questioned.