An improved bone marrow biopsy instrument is disclosed. The instrument comprises an elongate hollow alignment needle having a point which will advantageously penetrate soft tissue and indent bone surfaces. A rotatable bone cutting cannula is insertable within the alignment needle lumen.In use, the alignment needle is inserted through soft tissue overlying the bone from which a biopsy specimen is to be removed. Upon encountering the bone, linear pressure is exerted to indent the bone surface. The indent serves to hold the aligning needle in position and to provide an initial cutting surface. The bone cutting cannula is then inserted within the lumen of the aligning needle until it reaches the indent area. Rotation of the bone cutting cannula cuts through the bone periosteum and cortex to give access to the medullary cavity of the bone. The bone cutting cannula is then withdrawn and replaced with an appropriate marrow tissue cutting and collecting cannula or marrow blood collection syringe.