A theoretical approach for estimation of the drag correlation coefficients in the flow of Newtonian or weak non-Newtonian liquids around spherical solid particles is presented. Some new analytical relations are derived by using a stream function and the energy dissipation equation to approximate the drag coefficients to the experimental data. It is shown that these relationships can be applicable in a wide range of Reynolds number, Re, up to Re < 1000 for the liquids with a flow behavior index, n, in the range of 0.5 < n < 1. The predicted coefficients from these relationships are in very good agreement with the experimental data given in the literature. (C) 1999 Elsevier Science S.A. All rights reserved.