A 23-year-old female patient was diagnosed as having Hodgkin lymphoma (mixed cellularity type, clinical stage III B) in September 2000. She underwent ABVD chemotherapy and irradiation of a mediastinal lesion, resulting in complete remission. However, the disease reoccurred three month after the completion of initial treatment. She was admitted to our hospital for allogeneic stem cell transplantation. Thoractic vertebra, lumbar vertebra and iliac bone lesions were detected by FDG-PET, and a diagnosis of bone marrow infiltration was made. She received re-induction chemotherapy but did not achieve complete remission. A residual lesion in her bone marrow was detected by FDG-PET. She underwent unrelated allogeneic bone marrow transplantation in May 2002. Preconditioning was VP-16, CY and TBI. Engraftment of white blood cells was on day 15. Skin GVHD was detected at the same time and she was treated with steroid hormones, resulting in improvement. No residual mass could be detected by FDG-PET on day 60. However, she suffered from fever on day 80. Aggravation of the disease was revealed and she died from progression of the disease on day 120. FDG-PET is useful for the monitoring disease status and for determining the optimal timing of various treatments.