The design of two-phase flow lines for geothermal applications requires reliable information about main flow parameters. In the present work a one-dimensional, steady-state model for the computation of hold-up and pressure losses in horizontal and near-horizontal pipes is presented. The model is based on a mechanistic analysis of Stratified, Intermittent and Bubbly flow. The model has been implemented in the two-phase flow simulator, HORF, which has been developed in order to predict pressure losses relative to pipeline flow of geothermal brines. It is shown that the predictions are in very good agreement with field data obtained at Latera geothermal field, in Italy, relative to a flow line 2400 m long, and 18＇＇ nominal diameter.