A 61-year-old man with multiple myeloma (IgG-κ) received autologous peripheral blood stem cell transplantation (PBSCT) after induction of VAD in July 2009, and obtained a very good partial response. In November 2009, he was admitted to our hospital because of adenovirus-induced hemorrhagic cystitis and pneumocystis jiroveci pneumonia. The pneumonia resolved with sulfamethoxazole and steroid pulse therapy, and cystitis subsided spontaneously. In December 2009, serum protein electrophoresis showed two abnormal protein bands (APB)(IgG-λ, IgA-λ), different from the original M-protein, and IgG thereafter increased to 2,771 mg/dl with a concomitant increase in anti-adenovirus antibody to 4,096. In October 2010, APB disappeared. To date, he has been in stable complete remission for five years since PBSCT. The emergence of APB is considered to be a surrogate marker for long-term remission. Immune reconstitution syndrome and APB after high dose chemotherapy following PBSCT are discussed herein.