The characteristics of two-phase flow in a gas-assisted capillary tube were studied by experimental and numerical methods. Experiments were performed with five test fluids including two Newtonian fluids and three suspensions having yield stresses. The coating thickness of the fluids deposited on the tube wall was measured with the various fraction of the capillary volume occupied by the fluids. The fractional coverage increased monotonically as capillary number increased at low capillary number (Ca < 1), approaching an asymptotic value of 0.60 at high capillary number. The shape of the front and fractional coverage as a function of the capillary number could be obtained by numerical simulation based on a finite element method using Polyflow((R)) software. It was found that the predicted results are in good agreement with the experimental results. (C) 2003 Wiley Periodicals, Inc.