This method describes a procedure for determining the viscosity of 0.5% cellulose solutions, using 0.5M cupriethylenediamine as a solvent and a capillary viscometer. Measurements may be made on bleached cotton and wood pulps. Conventional kraft pulps with up to 4% lignin, as defined by TAPPI T 222 "Acid-Insoluble Lignin in Wood and Pulp" can also be analyzed. The applicability of this procedure to extended delignification pulps has not been determined.