Particle deposition in a tube with an abrupt contraction has been studied numerically and the results compared with available experimental data. A two-dimensional fully developed flow field in cylindrical coordinates was obtained by solving the Navier-Stokes equations numerically using SIMPLE, a computer program developed by Patankar (1980). Particles are deposited on the contraction due to inertial impaction and interception. The deposition efficiency was calculated by tracing particle trajectories in the flow field. Through parametric studies, a general correlation curve, giving the deposition efficiency as a function of modified Stokes number [η′ = 1 - exp (1.721 - 8.557x + 2.227x2)] was obtained to characterize particle deposition in the abrupt contraction. The theoretical models were found to agree well with available experimental data and were applied successfully in predicting particle deposition in various practical sampling systems.