Renal transplant recipients who have skin cancer potentially related to human papillomavirus were HLA typed with a special focus on HLA-A11, which in nonimmunosuppressed patients is negatively associated with the occurrence of virus-related carcinoma of the cervix. We found also a negative association between HLA-A11 and skin cancer; none of the 66 transplant recipients with skin cancer were positive for HLA-A11. As HLA-A11 seems to have a protective effect against skin cancer, we speculate that antigens induced by squamous cell carcinomas and possibly also by human papillomavirus may be efficiently presented through HLA-A11 to cytotoxic T cells. We also investigated a possible influence of other HLA alleles on the susceptibility of renal transplant recipients to skin cancer. The frequency of HLA-B27 was significantly higher in the transplant recipients with skin cancer, with a relative risk of 3.4 relative to healthy controls. No significant differences were found for other HLA class I or class II antigens.