The interpolyelectrolyte reaction between chitosan hydrochloride (CHI) and sodium polygalacturonate (NaPGA) has been investigated by conductimetric measurements. The composition of the reaction mixture, Z, was assessed by monitoring the conductivity when a CHI solution was added to a solution of NaPGA, It was determined to be unity at the equivalence point, indicating a 1:1 stoichiometry for the complex. The degree of complexation, theta, expressed as the fraction of groups reacted, was also obtained from the conductimetric measurements by means of a simple procedure. To this end the limiting ionic conductivities and transport coefficients of CHI and NaPGA were previously evaluated. It was found that theta varies with Z. It falls from unity to almost 0.8 as Z increases from 0.2 to 0.5 and then rises again up to 0.85 for Z = 1.