Particle deposition and suspension in a horizontal pipe flow have been studied. A 3D numerical multiphase mixture model available in Fluent 6.0 is used. The model solves continuity and momentum equations for the mixture and volume fraction equations for the secondary phases. Transport equations were also solved for turbulence parameters of the particulate phases. Gravitational and hydrodynamic drag forces were included. The deposition was studied as a function of particle diameter, density and velocity of fluid. The deposition of particles, along the periphery of the wall, at different depths was also investigated. The deposition of heavier particles at the bottom of the pipe wall was found to be higher at lower velocities and lower at higher velocities. The lighter particles were found to remain mostly suspended with homogenous distribution. Smaller particles also remained suspended with marginal higher concentration near the bottom of the wall. This marginal higher concentration of the smaller particles was found to be slightly pronounced for lower velocity. The larger particles clearly showed deposition near the bottom of the wall. This deposition was found to be pronounced at higher velocity.