In this work, it is shown that quadratic approximations of the function that relates the viscosity of polymer solutions with the polymer concentration lead to values of the intrinsic viscosity that are much more uncertain than the values obtained through simpler linear fits. Therefore, in spite of the expected better interpolations provided by second-order approximations, statistical arguments show that the use of linear fits is advisable when the number of experimental points available for the determination of intrinsic viscosities is small. Experimental data available for solutions of poly(4,4/-diphenylether-1,3,4-oxadiazole)s, POD-DPE, in sulfuric acid are used to illustrate this point. (C) 2000 Elsevier Science Ltd. All rights reserved.