A Joint Industry Project to investigate paraffin deposition in multiphase flowlines and wellbores was initiated at The University of Tulsa in May 1995. As part of this JIP, a computer program, based on the molecular diffusion theory, was developed for prediction of wax deposition during multiphase flow in pipelines and wellbores. The program is modular in structure and assumes a steady-state, one-dimensional flow, energy conservation principle. This paper will describe the simulator developed for predicting paraffin deposition during multiphase flow that includes coupling of multiphase fluid flow, solid-liquid-vapor thermodynamics, multiphase heat transfer, and flow pattern-dependent paraffin deposition. Predictions of the simulator are compared and tuned to the experimental data by adjusting the film heat transfer and diffusion coefficients and the thermal conductivity of the wax deposit.