125I-labelled haemagglutinin (HA) micropeptide mapping and haemagglutinin inhibition (HAI) tests with monoclonal antibodies were used in analysing antigenic variation of six strains of influenza A virus isolated from 1972 to 1983 in China. The results from micropeptide mapping generally coincided with those of sequence analysis. 125I-labelled HA micropeptide mapping is a simple, reproducible and practical method for surveillance of influenza, especially in combination with HAI test using monoclonal antibodies.