The taxonomic position of a Gram-positive coccus, designated strain CAU 28T, isolated from activated sludge foam was determined by using a polyphasic approach. Based on its cellular morphology and the results of biochemical tests, strain CAU 28T was identified tentatively as a member of the genus Lactococcus. Comparative 16S rRNA gene sequence analysis showed that levels of similarity between strain CAU 28T and the type strains of recognized Lactococcus species ranged from 90. 4 to 97.2 %. DNA-DNA hybridization studies showed that strain CAU 28T displayed less than 26.1 % relatedness to the type strains of recognized Lactococcus species. The rep-PCR fingerprints revealed that strain CAU 28T was well separated from reference Lactococcus species. The combined genotypic and phenotypic data indicate that strain CAU 28T represents a novel species of the genus Lactococcus, for which the name Lactococcus chungangensis sp. nov. is proposed. The type strain is CAU 28T (=KCTC 13185T =CCUG 55099T).