The phenomenon of lateral migration of neutrally buoyant rigid spheres is studied experimentally for Poiseuille Flow. The study relied on the particle migration technique to capture the distribution of particles radial position at different flow parameters. In this thesis, the varying experimental parameters are flow Reynolds number and particle concentration. These two parameters have been reported to have an opposing effect on the migration. Reynolds number is varying at Re=200-1200 and the particle concentration at φ = 0.05-0.5% . The results reveal that an increase in Reynolds number and particle concentration causes the migration to develop at a longer distance from the inlet. The migration is said to be developed when the particles have migrated to the region between the tube-axis and tube-wall. An increase in particle concentration shows a similar effect with the Reynolds number on the migration which the migration develop at a longer distance. An interesting result occurred at high particle concentration, at which the significance of the Reynolds number in altering the migration is decreasing. The study is also conducted to the secondary phenomena following the migration, the generation of inner annulus and the formation of trains of particles. It is shown that the variation of Reynolds number and particle concentration are significantly affected these secondary phenomena.