Fusobacterium necrophorum biovar A and biovar B were examined for haemagglutinability and ability to adhere to cells. Six biovar A strains agglutinated tannic-acid-treated chicken erythrocytes (1/32-1/64), as well as untreated chicken erythrocytes (1/16-1/64). They adhered well to MDBK and FL cells. Haemagglutination by them was not inhibited with D-mannose. In six biovar B strains, the haemagglutination titre was low for chicken erythrocytes and showed no increase for tannic-acid-treated chicken erythrocytes. These strains exhibited a weak ability to adhere to MDBK and FL cells.