The problem of osteoporosis is world-wide in people above 50 years of age. As this period is also a risk period for the development of multiple myeloma or other malignant processes, comprehensive differential diagnosis of malignant and benign osteoporosis is essential. By retrospective analysis of a 12-year group of 270 patients treated by chemotherapy on account of multiple myeloma the authors selected a group of 151 patients treated in addition to chemotherapy and immunomodulating drugs (mixture of proteolytic enzymes-Wobe Mugos) for 2-3 years, also with biphosphonates. At the time ofdiagnosis osteoporosis was in 24.5% patients the only finding on bones. When biphosphonates (Bonefos, Ibandronate) and chemotherapy were administered during a three-year observation period the bone process was stable in 61.59%, osseous changes disappeared in 11.26% and progression of osteolysis was recorded in 27.15%. The objective of the work was to emphasize the importance of a correct diagnosis of osseous changes which can progress even in clinically asymptomatic myelomas.