We describe 11 patients first seen with symptoms or signs related to lymphoma predominantly or exclusively involving one or both kidneys. The patients were seven men and four women, aged 40–77 years (median, 67). Seven of them had one or more other prior (four), subsequent (two) or both simultaneous and subsequent (one) primary malignant or premalignant lesions. The presenting symptoms of the patients with lymphoma included local pain (five cases), loss of appetite or nausea (four cases), hematuria (two cases), weight loss (two cases) or malaise (two cases). One patient had renal failure at presentation. One lymphoma was an incidental finding at the time of aneurysm resection. Nine patients had unilateral disease: two patients had bilateral disease. Six unilateral cases were initially considered on clinical (five) or clinical and pathological (one) evaluation to be primary carcinomas of the kidney. Gross examination of nephrectomy specimens revealed fleshy or firm, yellow, tan, or gray tumors form 5.7 to 22 cm (median. 7.5) in greatest dimensions that frequently invaded perinephric fat and adjacent structures. The lymphomas were subclassified as diffuse large cell (seven cases), follicular and diffuse large cell (one case), small lymphocytic plasmacytoid (two cases), and small noncleaved cell lymphoma (non-Burkitt's type) (one case). Immunophenotyping in nine cases revealed that all were B-lineage tumors. Three patients had Ann Arbor stage 1 disease, three had stage II, and five had stage IV. On follow-up, ranging from 1 week to 169 months (median, 15 months), 5 patients were alive and free of lymphoma. Four patients died of progressive disease 1 week to 23 months after diagnosis. One patient is alive at 4 months but has not completed chemotherapy. One asymptomatic patient has not been treated. Renal lymphomas are predominantly large-cell lymphomas of B-lineage affecting middle-aged and older adults and often can be treated successfully. Both clinically and pathologically, they can be mistaken for carcinomas of the kidney. A high proportion of patients in this series had malignant tumors of other types.