Adherent peripheral blood mononuclear cell-derived dendritic cells pulsed with autologous idiotypic protein (Id) were given to a patient with advanced-stage refractory myeloma. Potentially beneficial antimyeloma Id-specific immune responses were produced, characterized by MHC-dependent T-cell-proliferative responses with cytokine release and the production of anti-Id antibodies. A T-cell line generated after vaccination was also able to lyse autologous Id-pulsed targets and recognize fresh autologous myeloma cells. The immune responses were associated with a transient minor fall in the serum Id level and were not ablated by high-dose myeloablative chemotherapy. This report therefore demonstrates the clinical use of adherent peripheral blood mononuclear cell-derived dendritic cells for vaccination in cancer and the persistence of immune responses after high-dose chemotherapy. Such a therapeutic approach may be useful in reducing the relapse rate in patients who have minimal residual disease after chemotherapy.