Lagos-Quintana et al. reported the cloning of miR-1b, miR-1c andmiR-1d. The mature processed miR sequences are identical apart from the3' residues (A in mir-1b, C in mir-1c and UU in mir-1d). The 3' residuesof both miR-1b and miR-1c conflict with the predicted stem-loop precursorsequence shown here and these sequences are not found in currentassemblies of human and mouse genomes. It is suggested that polyApolymerase may add 1-3 nts to the 3' end of the mature transcript (TomTuschl, pers. comm.). The common 21 nts of the 3 reported miR sequenceshave been rationalised here and named miR-1. There are 2 pairs oforthologous putative hairpin precursor structures named mir-1-1 (humanMIR:MI0000651, mouse MIR:MI0000139), and mir-1-2 (human MIR:MI0000437,mouse MIR:MI0000652). The mature sequence shown here represents the mostcommonly cloned form from large-scale cloning studies .