Psoriasis was recently accepted as an autoimmune T cell-mediated disease. Various autoimmune disease associations for psoriasis have been defined, including multiple sclerosis, a model autoimmune demyelinating neurologic disorder. In this study, the familial frequency of psoriasis in a Turkish multiple sclerosis cohort was investigated, and a higher frequency of psoriasis was found, supporting the presence of a complex background of autoimmunity underlying psoriasis.