Abstract: A surgical instrument for performing tissue biopsies with a single tissue penetration. The elongated instrument comprises a hollow aspirate needle for aspirating bone marrow fluid, a hollow biopsy needle telescoped within the aspirate needle, and a solid stylet removably telescoped within the biopsy needle, all of which coaxially fit together. The stylet comprises a sharp distal end extending outwardly from the biopsy needle for initially penetrating body tissue and occluding the interior of the biopsy needle. The biopsy needle comprises a distal end normally projecting from the aspirate needle for thereafter penetrating a bone and obtaining a solid bone marrow sample. The bulbous, biopsy needle distal end is sharpened for captivating a specimen. It has a pair of relief slots dividing it into bulbous halves that are compressed together when the needle coaxially moves through the aspirate needle after withdrawal from tissue.