This review of recent data on the techniques and results of spinal magnetic resonance imaging in plasma cell dyscrasias provides a basis for selecting those patients who are most likely to benefit from this investigation. Sagittal images should be obtained using T1-weighted spin-echo and T2-weighted gradient-echo sequences. Epiduritis is best detected on sagittal or axial images acquired after gadolinium injection using T1-weighted spin-echo or phase-opposed gradient-echo sequences. Among patients with symptomatic multiple myeloma, 80% have abnormal magnetic resonance images of the lower spine due to plasma cell infiltration and this proportion increases with the stage in the Durie and Salmon staging system. Bone marrow signal abnormalities can be focal, diffuse and homogeneous, or diffuse and variegated. Vertebral fractures due to spinal infiltration or osteoporosis are seen in 48% of cases and spinal canal narrowing with impingement of bone tumors or epiduritis on nervous structures in 20%. The response to chemotherapy as evaluated based on conventional criteria is fairly well correlated with changes in magnetic resonance imaging findings. Among asymptomatic multiple myeloma patients with normal roentgenograms, 50% have tumor-related abnormalities on magnetic resonance images of the lower spine, which are associated with an increased likelihood of rapid progression to symptomatic disease. Similarly, one third of patients with an apparently solitary plasmacytoma of bone have evidence of other plasma cell tumors on magnetic resonance images of the lower spine, and this finding is associated with persistence of monoclonal component production after irradiation therapy, which may be of adverse prognostic significance. Patients with monoclonal gammopathies of uncertain significance have no evidence of tumorous lesions on magnetic resonance images of the lower spine.