Thrombocytopenia and neutropenia are common among neonates in intensive care units. Bone marrow aspirations are sometimes performed as part of their evaluation. However, marrow biopsies have not been reported from living neonates. Since architecture and cellularity cannot generally be accurately assessed from marrow aspirates, we devised a biopsy technique which we successfully applied to five cytopenic neonates (three with severe persistent thrombocytopenia and two with idiopathic neutropenia). This technique used a 19 gauge, half-inch Osgood needle to obtain bone marrow clots from the tibias of small preterm neonates which enabled the assessment of marrow cellularity and architecture. On the basis of our initial experience we have ceased using the traditional bone marrow aspiration technique in neonates and now use this technique exclusively.