We report a case of disseminated toxoplasmosis occurring 12 months after allogeneic BMT. The patient was seropositive for Toxoplasma gondii, and the donor was seronegative, so the patient was given anti-Toxoplasma prophylaxis. One year after BMT, he developed fever and muscle pain without other clinical symptoms. PCR amplification for T. gondii performed on blood was positive. Toxoplasma were found in bronchoalveolar lavage by PCR and in the marrow by special stains. With treatment, the PCR signal disappeared in 3 days while clinical symptoms resolved over 15 days. This case emphasizes the possibility of late toxoplasmosis after BMT despite prophylatic treatment, and the value of PCR in making the diagnosis.