Analysis of comparative surveillance on influenza carried out in the USSR and the GDR is presented. It was shown that both in the nonepidemic and epidemic seasons the incidence of influenza in the USSR increased considerably earlier than in the GDR. In the nonepidemic season of 1978-1979, strains of different antigenic structure were in circulation in the USSR and the GDR, whereas the epidemic of 1979-1980 was induced by new drift variants of A(H3N2) virus, A/Bangkok/1/79 and A/Bangkok/2/79. The epidemic strains circulating in both countries were dissimilar biologically and antigenically. In the nonepidemic period in the USSR and GDR the circulating A(H1N1) strains were represented not only by drift variants A/USSR/90/77 and A/Brazil/11/78 but also by natural recombinants of A(H1N1), A/USSR/61/79, in which the internal proteins (P, NP, NS, and M) were analogous to those of A(H3N2).