Cadmium(II) or lead(II) complex formation with an insoluble cross-linked poly(acrylic acid) was investigated in dilute aqueous solution (NaNO3 0.1 M, 25°C). Potentiometric titrations were carried out to determine the stability constants of the MA and MA2 complex species formed. The Bjerrum's method, modified by Gregor et al. (1955), for the study of polymeric acids was used. The results obtained showed that lead(II) was more readily bound to the polymer. PbA2 was the predominant species; the global stability constant log B102 was equal to 7.4. With cadmium(II), none of the complex species MA or MA2 was predominant (log B102 = 6.0). Finally, the comparison of these results with those of our previous studies showed that the insoluble cross-linked poly(acrylic acid) and its hydrosoluble linear analogues present similar complexing properties towards cadmium(II), lead(II), copper(II), and nickel(II).Key words: insoluble cross-linked poly(acrylic acid), cadmium(II), lead(II), complexation, potentiometry.