Ribotyping has been evaluated as a taxonomic tool for studying bacteria belonging to the Nocardia asteroides complex. The probe used was obtained by PCR from DNA extracted from the type strain Nocardia asteroides ATCC 19247, a sequence that codes partly for 16S rRNA. Interpretation of hybridization after EcoRI restriction of total DNA of 21 strains of the N. asteroides complex allowed for the identification of only four different ribotypes: two related to N. asteroides sensu stricto, one related to N. farcinica and one related to N. nova. These results confirm the classification established by Tsukamura in 1982 (M. Tsukamura, Microbiol. Immunol. 26:1101-1119, 1982) as well as the heterogeneity of N. asteroides sensu stricto species. Ribotyping may also provide a major identification technique for the species belonging to the N. asteroides complex.