Influenza B/Ann Arbor/1/86 is representative of antigenic variants responsible for the most important influenza epidemics during the 1985/1986 season. The nucleotide sequence of the hemagglutinin HA1 region and the deduced amino acid sequence are presented. Compared to the previous winter's vaccine strain B/USSR/100/83, B/AA/1/86 possesses 18 amino acid substitutions and 2 amino acid insertions, 50% of which are distributed within the vicinity of the reported single immunodominant antigenic site.