This paper presents the results of a study of the transient performance of a horizontal well that has been completed using Inflow Control Devices (ICD's) to modify the inflow profile along the wellbore to minimize the risk of premature gas or water breakthrough into the well. A realistic pressure and rate-transient design and interpretation computational model was developed and utilized in this study. The mathematical model has been used to evaluate the transient performance of a horizontal wellbore in single and dual porosity reservoirs. The horizontal well model utilized in this paper considers the wellbore to be finite-conductivity and assumes that the well has been completed using ICD's to control the inflow rates of fluids along the wellbore. The ICD's may be installed in selectively completed intervals of the wellbore of varying lengths and number, including variation in the number and sizes of nozzles and perforations in each of the completed intervals. A wellbore outflow production systems analysis was also included in the model in order to design or evaluate the performance of a horizontal well using various lengths, grades, and weights of production tubular goods, and for varying surface operating conditions.