Previous epidemiological studies showed an increased risk for the development of renal cell carcinoma (RCC) after adjuvant therapy or simultaneous discovery of non-Hodgkin's lymphoma (NHL). However, clinicopathological features of NHL complicated by RCC are not well known. We summarized the clinicopathological features of 42 cases with malignant lymphoma complicated by renal tumors collected in a nationwide study in Japan. There were 27 males and 15 females, and the age at initial diagnosis of NHL ranged from 51 to 85 years (median 69 years). The clinical stages of NHL were stage I in 13 patients, stage II in 8, stage III in 8 and stage IV in 13 patients. RCC was simultaneously detected in 4 patients, within 1 year after the diagnosis of NHL in 20 and after more than 1 year in 13 patients. In the remaining 3 patients, NHL was diagnosed 1 year (2 cases) or 6 years (1 case) after nephrectomy. Histologically, all but 2 cases of NHL were diagnosed as diffuse lymphoma, with the large-cell type being the most common. The remaining 2 cases were follicular lymphoma. NHL in 35 cases (85%) were immunophenotyped as B cell type and 4 (10%) as T cell type. Renal tumors in all but 2 cases were classified as RCC: clear-cell type in 29, chromophobic type in 3, chromophilic type in 7 and Bellini duct carcinoma in 1 case. All RCC showed a cellular malignancy of grade II or III. When compared to sporadic autopsy cases of NHL in Japan, the frequency of extranodal lymphoma and B cell type was higher in the current cases (p = 0.06). In addition, leiomyosarcoma occasionally occurred among complicated renal tumors.