The performance of oil wells producing during boundary-dominated flow was investigated to develop a better understanding of multiphase flow and its effects on single the performance. This understanding can assist the petroleum engineer in predicting the pressure-production behavior of oil wells producing under boundary-dominated flow conditions. An analytical inflow performance relationship (IPR) was developed from the multiphase flow equations. This relationship is based on the physical nature of the multiphase flow system and contributes to a better understanding of the pressure-production behavior of an individual well. The analytical IPR was verified using simulator information and provides a method for the petroleum engineer to develop individual IPRs for each reservoir.