Complete 16S rRNA gene sequences of three representative strains of anaerobic, Gram-negative, pigmented, moderately saccharolytic, indole-positive bacteria isolated from the oral cavity of humans were determined. According to comparative analyses of the rRNA sequence data, this organism represents a previously unknown species within the genus Prevotella. In addition, 22 representative strains and 21 reference strains (including 11 Prevotella intermedia and 10 Prevotella nigrescens strains) were subjected to multilocus enzyme electrophoretic analysis. The strains were consistently separated into three clearly distinct groups, corresponding to their previous entities. On the basis of the present phylogenetic results that confirmed our biochemical and genetic data, we propose a new species, Prevotella pallens. The type strain is NCTC 13042 (= AHN 10371).