The steady and dynamic shear properties of three different non-Newtonian fluids (an Acrysol TT615 solution, a 50% creosote-in-water emulsion and a Separan AP-30 solution) are determined. Their flow behaviour through tubes with abrupt expansions and contractions (＇square wave tubes＇) is investigated. The steady shear viscosity of these fluids can be described with a modified Quemada model. The geometric parameter method proposed previously by Kozicki et al. for duct of arbitrary cross section can be extended to the present systems with the use of a volume-average diameter. Flow in square wave tubes can be readily obtained from the straight capillary data by means of a shift factor (a + b). The shift factor is related to a pressure-average diameter. Conversely, using the pressure-average diameter eliminates the necessity of the shift factor. Corrections of inertial and entrance effects from Newtonian results can be approximately applied to non-Newtonian results. These corrections are relatively insignificant as compared with the effects of fluid elasticity and elongational-viscosity for viscoelastic fluids.