Conservation of microRNAs (miRNAs) among species suggests that they bear conserved biological functions. However, sequencing of new miRNAs has not always been accompanied by a search for orthologues in other spe-cies. I report herein the results of a systematic search for interspecies ortho-logues of miRNA precursors, leading to the identification of 35 human and 45 mouse new putative miRNA genes. MicroRNA tracks were written to visualize miRNAs in human and mouse genomes on the UCSC Genome Browser
