To obtain the subject composition without the need of any blending process, comprising an aqueous dispersion of a selfcrosslinking cationic polymer, and having such advantages as to improve the properties of electrodeposition bath and enable wider control of the design of the resulting crosslinked film.

First, an epoxide-functional prepolymer having polyepoxide (pref. diepoxide, esp. bisphenol A diglycidyl ether) and chainextended segments (each of the segments possesses at least one pendant hydroxyalkyl carbamate group) are formed; subsequently, the epoxide group of the prepolymer is reacted with an amine compound bearing at least one epoxide-reactive group and at least one blocked primary amino group to form a polymer; the amino group is then deblocked and at least partially neutralized prior to or during addition of water enough to prepare a dispersion of the polymer, then preparing an aqueous dispersion of the polymer, thus obtaining the objective composition.