An unusual case of the simultaneous occurrence of prostate cancer and IgE myeloma is reported. A 74-year-old man with urinary disturbance and elevated serum prostate-specific antigen level, of 7.4 ng/ml, showed Bence-Jones protein in the urine. Immunoelectrophoresis of the serum showed elevation of IgE kappa monoclonal protein. Radical prostatectomy was performed as a curative therapy for T1c, Gleason 3-2 prostate cancer. The patient has remained free of progression of both the myeloma and the prostate cancer for 26 months after the initial diagnosis.