Couple 1: A 74-year-old woman was diagnosed as having diffuse large B-cell lymphoma (DLBL) by left axillary lymph node biopsy. About 6 months later, DLBL was also diagnosed in her 79-year-old husband by right submandibular lymph node biopsy. Although the wife achieved partial remission with chemotherapy, she died due to disease progression. The husband's disease was chemotherapy-resistant, and he died of renal failure. Couple 2: An 86-year-old man was diagnosed as having DLBL by left axillary lymph node biopsy. About 4 years later, DLBL was also diagnosed in his 86-year-old wife by left axillary lymph node biopsy. Both the husband and the wife received chemotherapy. The husband is currently alive in complete remission, and although the wife achieved partial remission, she died due to disease progression. In both of these couples, it was considered unlikely that Epstein-Barr virus or human T-cell lymphotropic virus type I was related to the development of non-Hodgkin's lymphoma, and no environmental factors were confirmed to be involved. It is postulated that other unknown factors or agents may be associated with the development of lymphoma in married couples.