Multiple myeloma is a hematologic B-cell malignancy associated with elevatedserum and urine immunoglobuline, plasma cell infiltration of bone marrow,soft-tissuePlasmacytomas and skeletal complications.The important point is to differentiat between two other types of plasma cell disorder whichare MGUS and solitary plasmacytoma, both have no sign and symptoms and no need treatmentjust follow up.The recent way to diagnosis and detect transformation from benign disease(MGUS) to MMis a serum-based assay called FREELIT, which detects and quantifies free light chains(those not associated with intact immunoglobulin), has recently become available. Evidencesuggests that this test may help predict the risk of progression from monoclonal gammopathyof undetermined significance (MGUS) to multiple myelomaThe understanding of biology of MM and mechanism of drug resistance have share in arrivalof novel agents as Bortezomib ,Thalidomide and its analoges which are very effective intreatment of newly diagnosed cases and also in refractory-relapsed one.