HLA DR frequencies of patients with multiple non-melanoma skin cancers were analysed. There were significant differences in the frequencies of HLA DR1 DR4 and DR7 between patients who only had basal cell carcinomas and patients who had both basal and squamous cell carcinomas. There were significant differences in the frequency of HLA DR53 between the two groups. This antigen is in linkage disequilibrium with HLA DR4 and DR7, and it is not possible to distinguish the primary susceptibility locus.