It was found that p-aminostyrene (PAS) could be oligomerized by using several aminium perchlorates as catalysts in acetonitrile to give a dimer D in the initial stage of the reaction and finally the isomerization oligomer 1 at the end, in quite similar manner to the preceding paper (1), where dimerization (hydroamination) is the main reaction in the initial stage. The pK(a) values for the amines were evaluated by the indicator method, and the [H+](0) and [MH+](0) values were calculated from equilibrium equations. As a result the rate increased with decreasing pK(a) of the catalytic amine used and reached an overall constant value. From the relationships between the rate of the reaction and the [H+](0) or [MH+](0) values calculated numerically, however, it was determined that the rate was more affected by the [H+](0) or [MH+](0) values rather than the pKa of the catalyst It was assumed that the reaction would be initiated by the electrophilic attack of MH+ on the double bond of the monomer. Three successive reactions were proposed for the dimerization step: slow protonation followed by subsequent fast reactions; amine addition to the resultant styryl cation and proton elimination. It was assumed that oligomerization might proceed via the same three successive reactions as proposed for the dimerization step.