The objective of this work is to identify the best location to install oil mills to process vegetable oil, obtained from castor, in the North Central Region in the State of Bahia, Brazil. Fifty five cities in that region have been identified as producers of this vegetable as so as their respective productivity and distance between them and the cities for the installation of the oil mills. Besides, the city of Candeias was elected to receive the produced oil, since there is a factory (PETROBRAS) that biodiesel castor oil. Aiming to encourage local small scale farming and processing of castor, produced at that region, two models of screw presses have been chosen, with capacities of 7.5 and 22.5 tons of castor’s oil per day to extract the oil. A mathematical model has been developed and, using the software XPRESS MP Release 2007, satisfactory results have been reached, that indicated eight cities for the installation of the mills.