The nucleotide sequences of the 16S ribosomal RNA gene (rDNA) of swine and ovine corynebacterial strains were determined. The sequences of the strains that identified as Corynebacterium pseudotuberculosis by their biochemical characteristics were homologous with each other. The phylogenetic position of C. pseudotuberculosis strains was closet to C. ulcerans and next closet to C. diphtheriae. The nucleotide sequence of another swine isolate, SC8, was similar to that of a recently proposed species, C. seminale, and a non-validated species, "C. glucuronolyticum," with about 0.01 to 0.02 evolutionary distances. Analysis of the predicted secondary structure of the 16S rRNA molecule agreed with the close phylogenetic relationships between C. pseudotuberculosis and C. ulcerans and between C. seminale and strain SC8.