Asaccharolytic, gram-negative, anaerobic vibrios, which require formate and fuma-rate for growth in broth culture have been isolated from plaque in gingival crevice of adults without periodontal disease. They were suspected to be Wolinella species phenotypically from guanine-plus-cytosine (G+C) contents. Seven isolates were compared with Wolinella curva ATCC 35224, Wolinella. recta ATCC 33238 and Wolinella succinogenes ATCC 29543 with respect to cellular and colonial morphologies, biochemical and serological characteristics, G+C content of DNAs, and DNA homology. Five strains were identified as W. curva, and the remaining two strains had some distinct features from all three species. The major distinctions were : 1) several flagella at one end of the cell observed by electron microscope; 2) biochemical and biological characteristics including ability to decompose H2O2, growth at 25°C, growth in the presence of sodium fluoride, and reduction of neutral red or benzyl viologen; 3) serological difference by whole cell agglutination tests; and 4) absence of DNA homology. We propose the name Wolinella curva subsp. intermedius as a new subspecies for these two strains.