Two bacterial isolates, strains IMMIB RIV-085(T) and IMMIB RIV-095, isolated from a blood-sucking bug of the genus Triatoma, were characterized by phenotypic and molecular taxonomic methods. Chemotaxonomic investigations revealed the presence of cell-wall chemotype IV and mycolic acids consistent with the genus Rhodococcus. Comparative 16S rRNA gene sequencing showed that the two isolates are genealogically highly related (100% sequence similarity) and constitute a new subline within the genus Rhodococcus, with Rhodococcus corynebacteroides and Rhodococcus rhodnii as their nearest phylogenetic neighbours (98.4 and 98.3% sequence similarity, respectively). However, DNA-DNA hybridization experiments demonstrated unambiguously that the isolates are genealogically distinct from R. corynebacteroides and R. rhodnii (32 and 43% relatedness, respectively). The isolates could be distinguished from their phylogenetic relatives and other members of the genus Rhodococcus by means of biochemical tests. On the basis of both phenotypic and phylogenetic evidence, it is proposed that these isolates be classified as a novel species, Rhodococcus triatomae sp. nov. The type strain is strain IMMIB RIV-085(T) (=CCUG 50202(T)=DSM 44892(T)).