A Linear programming (LP) model was used to select Egyptian Barki rams, in a production unit, under some constraints of resources and performance. Illustration was made to select among 4 rams (each ram had at least 11 lambs of 6 months of age per year) to maximize the annual gross margin, subsequently the net farm income. Model constraints were farm capacity (was available for only 300 ewes), total lambs weight at 6 months old (was 1500 kg/farm/year) and available labor (was 30000 hour/year). LP model modified using some mathematical equations under the same set of constraints in addition to feed constraint. The model input coefficients were selling lambs (price 20 LE/kg live body weight), paying feed (2.5 LE/kg dry matter intake) and paying labor (1.5 LE/hour) (farm gate price of Maryut research station, DesertResearchCenter, year 2004). The present results showed that there was a difference between the two decisions of rams selection under farm resources constraints using LP model which done according toabsolute kilogram yield of lambs at 6 months old. If the selection of ram was dependent only on kilograms produced at 6 months, rams were ranked as ram1, ram2, ram3 and ram4. While, selection according to LP solutions, which showing less opportunity cost, LE, the rank of rams were ram3, ram4, ram2 and ram1. The gross margin was 6497 LE and 5746 LE when keeping 8.22 and 7.72 lambs of the ram3 in LP model and LP modified model, respectively. These results were obtained under binding of the previous set of constraints. The results concluded that selection Barki rams should not be only according to the highest kilograms produced of their lambs at 6 months old but also, according to farm available resources.