MicroRNAs (miRNA) are short RNA molecules regulating the expression of specific mRNAs. We investigated the expression pattern and potential targets of mouse miR-140 and found that miR-140 is specifically expressed in cartilage tissues of mouse embryos during both long and flat bone development. MiR-140 expression was detected in the limbs of E11.5 embryos in the primorida of future bones both in the fore and hindlimb and across autopod, zeugopod and stylopod. All digits of E14.5 fore- and hindlimbs showed accumulation of miR-140, except the first digit of the hindlimb. MiR-140 expression was also detected in the cartilagenous base of E17.5 skulls and in the sternum, the proximal rib heads and the developing vertebral column of E15.5 embryos. A potential target of miR-140, histone deacetylase 4, was validated experimentally and the possible role of miR-140 in long bone development is discussed.