As a basis for understanding the complex problems of neoplastic development in plasma cells, several concepts emerging from the study of plasma cell tumor development in mice are presented. In the mouse there are five basic models of plasmacytomagenesis (Table 1), designated “spontaneous,” “peritoneal,” “accelerated,” “transgenic,” and “viral.” These systems are used throughout the discussion. After a brief summary, several questions pertaining to the process of plasmacytomagenesis will be discussed.