Abstract. In this paper, we investigate steady, viscous, incompressible fluid flow in an asymmetric channel with absorbing walls which may have possible applications in flows in renal tubules. The effect of fluid absorption through permeable wall is accounted for by prescribing flux as a function of axial distance. The nonlinear governing equations of motion are linearized by perturbation method by assuming δ (ratio of inlet width to wavelength) as a small parameter and the resulting equations are solved by numerical methods. The effects of reabsorption coefficient (α) and phase difference (φ) on the velocity profiles, mean pressure drop and wall shear stress are studied and explained graphically.