The study focused on market age, enterprise size and relative efficiency in broiler production in Imo State . The main aim was to determine resource use efficiencies in broiler brooding and rearing enterprises as well as large-scale and small-scale outfits in the two enterprises. Using multi-stage sampling technique, the study area was zoned into three using the existing zoning arrangement of the Imo State Agricultural Development Programme (ADP). A total of nine L.G.As were randomly selected and a total of 180 broiler farmers (made up of 90 brooders and 90 rearers) were selected. A set of structured questionnaire was administered on the farmers to obtain required information. Data were analysed using simple statistical tools, regression models, additive multiplicative dummy variable models, profit function technique and enterprise analysis. Results showed that broiler production was profitable but rearing birds to maturity was more profitable than brooding birds and selling at four weeks old.  Large-scale rearing of birds was more profitable than small-scale outfit. In brooding enterprise, no remarkable difference in profit margin existed between large-scale and smallscale. Broiler rearing farmers were found to be more technically efficient than the brooding farmers and small-scale rearers were more technically efficient than large-scale ones. The implication is that technical efficiency may not increase by increasing size of operation in rearing broiler. In brooding, large-scale outfit was more technically efficient than small-scale. Technical efficiency may be increased by increasing size of operation in broiler brooding business. None of the farmer groups achieved absolute allocative efficiency. They therefore did not maximize profit.  However brooding farmers were more allocatively efficient than the rearing farmers.  Large-scale rearers were more allocatively efficient while small-scale brooders were more allocatively efficient in brooding enterprise. The implication is that in broiler rearing business, allocative efficiency may be increased by increasing size of operation. Brooding farmers were found to be more economically efficient than rearing farmers.  Small-scale brooders were more economically efficient than large-scale counterpart. Allocative efficiency may not be increased by increasing size of operation in broiler brooding. None of the farmer groups operated at constant returns to scale.  Brooding farmers operated at increasing returns to scale while rearing farmers operated at decreasing returns to scale. Brooding farmers by operating at increasing returns to scale means that they grossly under-utilized resources, they had opportunity to increase output by increasing input use. The rearing farmers over-utilized some resources. It was recommended that farmers should brood and rear their stock to maturity to avail themselves the opportunity of allocative and economic efficiencies of brooding and technical efficiency and high profit margin of rearing.