A sensitive and simplified method of ~(125)I-labeled peptide mapping was used to estimate the rates of the haemagglutinin(HA) mutation of 5 strains of influenza Al viruses and 5 strains of influenza A3 viruses. It could be calculated that the average rates of HA mutation for these two subtypes of viruses are 0.47% and 0.44% per year respectively. The strains isolated in 1986 showed some specialities as compared with the average rates of HA mutation The relation between the rates of HA mutation and the epide...