Surfaces of a hydrolyzed PMDA-ODA polyimide have been examined by contact angle titrations. From an analysis of the data and the free energy changes occurring during ionization, an estimate can be made of the number of carboxylic acid groups created by hydrolysis. Calculations estimate that (5-7) x 10(17)-CO2H/m(2) are formed during alkaline hydrolysis (0.25 M NaOH) from times of 5-120 min, These results are consistent with X-ray scattering data and unit cell area values obtained on aromatic polyimides.