The relation of HAA carrier state to ABO and rhesus blood groups was investigated in a sample of 10,068 healthy Greek recruits. Although the frequency of HAA carriers was highest in the AB blood group, it did not differ significantly from the other ABO blood groups. No relation was found between rhesus blood group and HAA carrier state. It is suggested that factors closely associated with ABO and rhesus blood groups do not appear to be of importance for the genesis of the HAA carrier state.