The 60 kb [kilobase] circular mitochondrial genome of N. crassa contains a single transcription unit for 17S and 24S rRNA mapping within the largest Eco RI fragment E1 (19.6 kb). This fragment was isolated from uncloned mitochondrial DNA and further analyzed by cleavage with restriction endonucleases Hind II, Hind III, Bam HI, Pvu II and Bgl I, and by EM of rRNA/DNA hybrids. The resulting map shows a 2.3 kb intervening sequence interrupting the gene for 24S rRNA. The main part (2.7 kb) of this gene is separated from the 17S rRNA gene by a 5 kb segment which contains several transfer RNA genes. This segment is much longer than the putative 1 kb spacer sequence within the 32S precursor molecule for both rRNA, suggesting a second splicing event in that region.