The rare blood group antigen previously referred to as the 'Haakestad antigen' is shown to be identical with the Hov antigen (numerical designation: 700.038). Family studies add AB0 and HLA to the systems already known to segregate independently from Hov. Among 2,021 Danish blood donors, 4 Hov+ persons were found. Anti-Hov activity has been demonstrated in several 'multiple-antibody sera'.