Abstract: The invention relates to an instrument for bone marrow puncture comprising a sampling needle (10) fused to a piston which can be displaced within a piston barrel (4), a mechanism (6) for releasing the piston from a first position, at which the needle is entirely withdrawn within the interior of the anterior part of the said piston barrel, to a second position at which the extremity of the needle is projected to the outside. The stroke of the piston is sufficient for the needle to pierce the bone and reach the region of the bone marrow where sampling is to be carried out, when the anterior part (32) of the instrument is placed and maintained at the height of the appropriate bone. The posterior part of the piston barrel defines a closed chamber (16) for the collection of the marrow sample aspirated into this chamber under the effect of the negative pressure generated by the displacement of the piston from the first to the second position.