High-dose melphalan plus autologous stem-cell transplantation (ASCT) is a standard of care for transplant-eligible patients with newly diagnosed multiple myeloma (NDMM), and adequate hematopoietic stem-cell (HSC) collection is crucial to ensure hematologic recovery after ASCT. In this prospective, observational study we evaluated HSC mobilization with granulocyte colony-stimulating factor (G-CSF), cyclophosphamide, and 'on-demand' plerixafor (in patients with.