We have found that the catalytic RNA of RNase P of Escherichia coli (M1 RNA) can cleave 2S ribosomal RNA (2S rRNA) of Drosophila melanogaster at specific positions in vitro. The cleavage mainly occurred at two sites between nucleotides 11 and 12, and between 16 and 17 of 2S rRNA. Kinetic analyses of the reaction revealed that a dimer caused by intermolecular interaction of 2S rRNA may be the substrate for the cleavage between 11 and 12, while a simple monomer is the substrate for the cleavage between 16 and 17. Substrate recognition by M1 RNA is also discussed.