The monomer-monomer interaction plays important roles in many cases of alternating copolymerizations. This article describes first a review of alternating copolymerizations in terms of the varieties of the types of reactions,the types of monomers, and the combinations of monomers. The reactions of alternating copolymerizations are classified into the following five types; (i) free radical alternating copolymerization involving polar vinyl monomers (Type-1), (ii) free radical alternating copolymerization between olefins and acrylic monomers with the assistance of Lewis acids (Type-2), (iii) alternating copolymerization of olefins and diolefins with ZLegler-Natta catalysts (Type-31, (iv) ring-opening copolymerization of heterocyclic monomers (Type-41, and (v) spontaneous alternating copolymerization via zwitterion intermediates (Type-5).The monomers which have been involved in alternating copolymerizations are polar vinyl compounds, mono-olefins, diolefins, heterocyclic compounds, S02, C02 and isocyanates. Then, the general patterns of the mechanism of sequence control were described, and the detailed mechanisms were discussed in the copolymerizations of Types-1, -2 and -5 in which the monomermonomer interaction has been reported to be responsible for the initiation and the sequence regulation.