In the current study we analyzed genotypic frequencies of cytotoxic T-lymphocyte antigen-4 (CTLA-4)/CT60, CTLA-4/A49G, interleukin (IL)-4, and IL-10 polymorphisms in 117 renal cell carcinoma patients, 96 patients with colorectal cancer, and 196 healthy controls to test for an association between polymorphism in these genes and the risk of renal and colon cancer in a Spanish group of patients.