A method is proposed for the direct determination of the rate of shear‐shearing stress curve of a fluid from data obtained in concentric cylinder viscometers. The method involves the use of a viscometer in which the ratio of outer to inner cylinder radii can be varied. It is further shown that to a close approximation two such radius ratios are sufficient to define the flow curve.Data for two non‐Newtonian systems are presented to show that the proposed method is valid.