The polarographic behaviour of hydrolyzed propene-maleic anhydride copolymers in the interval pH 2.0-11.0 has been investigated by differential pulse polarography in aqueous lithium chloride solution at 25 degrees C. In dependence on the pH-value, one, two or three signals, belonging to the acid groups in the copolymer, appear in the polarograms. Three apparent polarographic acid constants have been determined graphically from the changes in the halfwave potential of the separate peaks in correlation with pH.