The haemagglutinin of A/Dk/alb/60/76, an influenza A virus isolated from feral ducks in Canada, possesses no antigenic relatedness to any of the 16 reference haemagglutinin subtypes. Results of serological tests (HI and double immunodiffusion) with monospecific antisera to the haemagglutinin of this virus indicate that it represents a new avian haemagglutinin subtype. We propose that this haemagglutinin be designated as Hav10 under the current system of nomenclature.