Multiple myeloma (MM) is characterized by a proliferation of plasma cells responsible for osteolytic lesions. Imaging studies are performed in MM to establish diagnosis and prognosis, and may also be used to judge the efficacy of treatment and to detect complications. TO ESTABLISH THE DIAGNOSIS: Conventional radiography demonstrates, at the time of diagnosis, characteristic features in 80% of cases. These lytic lesions involve more often the sites of red marrow. More rarely the only abnormal finding is diffuse osteopenia. Tomodensitometry and, above all, magnetic resonance imaging (MRI), which is a reference method for bone marrow disorders, can be useful for diagnosis in some difficult cases. But the lesions observed, hyposignals on spin echo T1 sequences and hyposignals on T2-weighted gradient echo, are not specific and usually do not allow to distinguish MM from osteolytic metastasis or other bone marrow disorders. TO DETERMINE EXTENT OF DISEASE AND TO EVALUATE PROGNOSIS: According to Durie and Salmon, the extension of home lesions at diagnosis is strongly correlated with the myelomatous measured cellular mass and with survival of patients. But this relation is denied by some authors who have noted that the shortest survival was seen in patients with normal X-rays. TO JUDGE THE EFFICACY OF TREATMENT: Improvement of the radiological abnormalities is observed in nearly 30% of patients responding to a conventional chemotherapy and appears to be an adverse pronostic sign. A good correlation between MRI and the biological response to treatment has also been reported. TO RECOGNIZE COMPLICATIONS OF DISEASE: Conventional radiography is also very important in diagnosis of complications like fractures or vertebral compression. Lastly, MRI is the investigation of first choice in the evaluation of patients with suspected spinal cord compression.