PURPOSE Prognostic Immunophenotyping in Myeloma Response (PRIMeR) is an ancillary study of minimal residual disease (MRD) assessment for multiple myeloma by next-generation multiparameter flow cytometry (MFC). Patients were enrolled on a three-arm randomized control trial (Blood and Marrow Transplants Clinical Trials Network 0702 Stem Cell Transplant for Myeloma in Combination of Novel Agents [STaMINA]; ClinicalTrials.gov identifier: NCT01109004). METHODS Four hundred and thirty-five patients consented to the MRD panel, which included 10 monoclonal antibodies measured via six-color MFC. MRD was measured at baseline/preautologous hematopoietic cell transplant (BL/preAutoHCT), premaintenance (PM), and 1 year (Y1) after AutoHCT with a sensitivity of 10–5 to 10–6. The primary objective was to assess MRD-negative (MRDneg) at 1 year after AutoHCT and progression-free survival and overall survival (PFS/OS). RESULTS Similar to the STaMINA results, at a median follow-up of 70 months, there was