AbstractThe flow of various fluids of different rheological behaviour has been studied in both fixed and fluidized beds. These fluids were water and aqueous solutions of glycerin, Carbopol and Separan AP‐30. For small Deborah numbers, the flow of Carbopol and Separan AP‐30 solutions thorough fixed beds is well described by the Ergun relation using the generalized Reynolds number of Christopher and Middleman (1965). Deviations from this behaviour are observed in fluidized beds as preferential flow paths easily occur near the distributor. These deviations are small for Newtonian fluids but take more importance with non‐Newtonian solutions and are increased by viscoelast