These Clinical Practice Guidelines are endorsed by the Japanese Society of Medical Oncology (JSMO) incidence and epidemiology Multiple myeloma (MM) accounts for 1% of all cancers and ∼10% of all haematological malignancies. The incidence in Europe is 4.5–6.0/100 000/year with a median age at diagnosis of between 65 and 70 years; the mortality is 4.1/100 000/year. Almost all patients with MM evolve from an asymptomatic pre-malignant stage termed monoclonal gammopathy of undetermined significance (MGUS). MGUS progresses to MM at a rate of 1% per year. In some patients, an intermediate asymptomatic but more advanced pre-malignant stage termed smouldering (or indolent) multiple myeloma (SMM) can be recognised. SMM progresses to myeloma at a rate of 10% per year over the first 5 years following diagnosis, 3% per year over the following 5 years and 1.5% per year thereafter . diagnosis Diagnosis of MM should be based on the following tests:  -Detection and evaluation of the monoclonal (M-) component by serum and/or urine protein electrophoresis (concentrate of 24 h urine collection); nephelometric quantification of IgG, IgA and IgM immunoglobulins; characterisation of the heavy and light chains by immunofixation; and serum-free light-chain (FLC) measurement; -Evaluation of bone marrow (BM) plasma cell infiltration: BM aspiration and/or biopsies are the standard options to evaluate the number and characteristics. Moreover, the BM sample should be used for cytogenetic/fluorescence in situ hybridization (FISH) studies and also has the potential for immunophenotypic and molecular investigations; -Evaluation of lytic bone lesions: a radiological skeletal bone survey, including spine, pelvis, skull, humeri and femurs is necessary. A magnetic resonance imaging (MRI) or computed tomography (CT) scan may be needed to evaluate symptomatic bony sites, even if the skeletal survey is negative and the patient has symptoms suggesting bone lesions. Moreover, MRI provides greater detail and is recommended whenever spinal cord compression is suspected. Fluorodeoxyglucose positron emission tomography is currently under evaluation but should not be systematically used; -Complete blood cell count, with differential serum creatinine and calcium level.