AbstractThis paper describes a preliminary study of the linear flow of a non‐Newtonian fluid, a water solution of Dextra (a polysaccharide), in porous media. A modification of Darcy's law, which uses capillary rheology data, is developed to describe non‐Newtonian flow in underground reservoirs. The generalization, in effect, replaces the porous media with a capillary of equivalent radius proportional to the square root of the ratio of permeability to porosity. The constant of proportionality αoshould be independent of permeability and porosity for a given type of rock. This has been partially confirmed experimentally. In principle, a capillary rheogram and a single core test permit evaluation of αo. Then non‐Newtonian flow can be predicted in this type of rock regardless of porosity, permeability, or fl