Multiple myeloma is still a fatal disease. Despite advances in high-dose chemotherapy supported by autologous transplantations, relapse of the underlying disease remains the primary cause of treatment failure. Strategies for post-transplantation immunomodulation would be desirable for eradication of remaining tumor cells. Toward this end, immunotherapy aimed at inducing myeloma-specific immunity in patients has been exploited. Idiotype protein, secreted by myeloma cells, has been the main target for immunotherapy as it is the best-defined, tumor-specific antigen. The focus of this review article is the use of idiotype as a form of protein antigen to immunize patients, to load dendritic cells, or as part of DNA vaccines. Various strategies of immunotherapy and the outcome of clinical trials are also discussed.