The outcome of myeloma patients is highly heterogeneous, with survival ranging from a few months to more than 10 years. Accordingly, investigation of prognostic factors may contribute to identification of risk categories and to provision of more accurate information about individual disease outcome. For many years prognostic factors have relied on clinical parameters such as age, hemoglobin level and renal function. Subsequently, biological parameters such as the proliferative activity of plasma cells and beta2-microglobulin have been added to the prognostic arsenal. More recently, cytogenetic and molecular markers with significant influence on disease outcome have been identified. Here we will review the most relevant prognostic factors reported in the literature in patients treated with both conventional chemotherapy and high-dose therapy followed by autologous stem-cell support, as well as in asymptomatic MM and MGUS patients.