A model has been developed that allows the design of geothermal production wells. This design problem is quite complex because of the many physical and chemical phenomena that take place in the well bore, each of which has a significant influence on the well performance with respect to total flow rate of brine and steam, pressure loss up the well, or wellhead pressure available for the power producing system, scaling and plugging of the well due to chemical precipitates. The accuracy of the design predictions were determined by comparing them with new well test data developed as part of this project. The general theory behind two-phase flow phenomena and the theory that describes the operation of the model ere described in previous reports (1, 2). This report provides a final version of the computer code, called DEGEOWEL that accomplishes the calculations according to the model. This final version incorporates the preferred correlations developed under this project for determining the flow regime, holdup and frictional pressure drop in two-phase flow. [DJE-2005]