The nucleotide sequence of a DNA segment carrying the entire 15S rRNA gene of yeast mitochondrial genome was determined. Many stretches of sequence are present which are homologous to the Escherichia coli 16S rRNA gene. The gene sequence can be folded into a secondary structure according to the model on bacterial rRNA. The structure reveals a striking similarity between the 2 RNA despite the large difference in their base compositions. In the middle of the gene, a guanine-cytosine rich sequence was found that is also present in several other regions of the mitochondrial genome.