A case of urinary bladder carcinoma in a patient with malignant lymphoma (ML) involving the thyroid gland, gastrointestinal tract and the gallbladder is reported. The histological type of ML from the biopsy specimens of the thyroid gland and the stomach was non-Hodgkin's, diffuse large cell lymphoma of B cell origin. The patient had been treated for ML with cyclophosphamide (CPM), doxorubicin, vincristine and prednisolone effectively then maintained with low dose CPM. Two and a half years after the initial therapy, urinary bladder tumor diagnosed transitional cell carcinoma histologically was found. The patient had received 55 gr. of CPM totally. The dose of CPM was relatively smaller than the one in the other second cancer cases reported induced by CPM previously. It may be suggested that the urinary bladder carcinoma induced by CPM is related not only total dose of CPM but also the other factors. Thus usage of CPM must be cautious because of the secondary disease.