The nucleotide sequence of 5S rRNA from Mycoplasma capricolum is more similar to that of the gram-positive bacteria than that of the gram-negative bacteria. The presence of two copies of rRNA genes in M. capricolum genome has been demonstrated. The two different rRNA gene clusters have been cloned in E. coli plasmid vectors and analyzed for the rRNA gene organizations, demonstrating that the gene arrangement is in the order of 16S, 23S, and 5S rDNA. The ribosomes of M. capricolum contain about 30 species of proteins in 50S and 20 in 30S subunits. The number and size of the ribosomal proteins are not significantly different from those of other eubacterial ribosomes.