A novel mitotic stimulator of myeloid hematopoietic cells was prospectively evaluated to detect enhanced quantity and quality of metaphases from bone marrow (BM) cultures for cytogenetic analysis. This polydonor mixed lymphocyte conditioned (PMLC) media decreased the culture failure rate, improved detection of chromosomal aberrations, and reduced technologists' analysis time. The conditioned media is recommended as a highly effective culture system for normal and neoplastic cells of myeloid lineage.