The determination of acid end-groups of acrylamide and acrylonitrile polymers initiated by cerium (IV)-malonic acid, cerium (IV)-tartaric acid and cerium (IV)-citric acid redox initiators systems was made in aqueous and nonaqueous media potentiometrically. The effect of solvent, titrant and electrode system on the half-neutralization potentials and number-average molecular weights, ($) over bar M(n), were determined potentiometrically and were studied. These ($) over bar M(n) values were compared with those obtained by viscosimetric and conductometric methods.