About 5-10% of boys with acute lymphoblastic leukemia (ALL) present with isolated testicular relapse. Very frequently these relapses occur during treatment or in the following six months, and in these cases the prognosis is very severe. The patients are usually treated with radiotherapy and chemotherapy or bone marrow transplantation (BMT). Testicular relapses after BMT are relatively rare. We report the case of a child with ALL who presented testicular relapse during therapy and was treated with local radiotherapy (2000 cGy), chemotherapy and allogeneic matched BMT. The preparative regimen consisted of Cyclophosphamide (60 mg/kg/day x 2 days) and total body irradiation (200 cGy x 2/day x 3 days). Engraftment was documented at day + 14. The patient presented again with testicular relapse at day + 146, and was therefore treated with orchiectomy, local radiotherapy and systemic chemotherapy. A marrow relapse followed, however, at day + 284 and the patient died of progressive disease.