Multiple myelomas are a less frequent cancer site among both sexes. On a worldwide scale, it is estimated that about 86 000 incident cases occur annually, accounting for about 0.8% of all new cancer cases. About 63 000 subjects are reported to die from the disease each year, accounting for 0.9% of all cancer deaths. Geographically, the frequency is very unevenly distributed in the world with the highest incidence in the industrialised regions of Australia / New Zealand, Europe and North America. Incidence and mortality seem to be stable in Asian countries and to increase slowly over the decades among whites in the western countries. The etiology is poorly understood. This depends partly upon the fact that the risk factors which play a major role for malignant diseases in general, such as tobacco consumption and diet have not been found strongly involved into multiple myeloma etiology. Nevertheless, some consistency seems to be in the findings about a risk elevation with obesity and a slightly decreased risk with high fruit consumption. Despite some contradicting results, indications to a role of ionising radiation persist. Finally, infections with HIV and hepatitis C virus appear related to an elevated multiple myeloma risk. Currently, large efforts are undertaken to unravel the etiology of malignant lymphoma including those of multiple myeloma.