The taxonomic position of two Tsukamurella strains isolated from activated sludge foam was clarified. The organisms, isolates JC85 and N1176T, were found to have chemical and morphological properties typical of members of the genus Tsukamurella. DNA-DNA relatedness studies showed that the strains formed a distinct genomic species that was most closely related to Tsukamurella spumae. The two isolates also share a range of phenotypic properties that distinguishes them from representatives of all species of Tsukamurella with validly published names. It is evident from the data that the two organisms should be classified as a novel Tsukamurella species, Tsukamurella pseudospumae sp. nov. The type strain is N1176T (=DSM 44118T=NCIMB 13963T).