Sequences homologous to the yeast mitochondrial structural genes for cytochrome oxidase subunits I and II, ATPase 6 and cytochrome b were identified on the kinetoplast DNA maxicircle molecule by low stringency hybridization of maxicircle blots with heterologous probes derived from mitochondrial DNA of yeast petite mutants. No hybridization was observed with the yeast ATPase 9 gene probe. The relative extent of base sequence mismatch was determined by melting of the heterologous hybrids. Candidates for the transcripts of these presumptive structural genes were proposed with reference to the transcriptional map of the maxicircle of Leishmania tarentolae. These results provide the first indication that maxicircle DNA specifies information for a limited number of conserved mitochondrial gene products similar to those already described for other eukaryotic cells.