Many autoimmune diseases have been associated with deficient serum 25–hydroxy vitamin D (25–(OH) D) level. Psoriasis now being proved as an autoimmune disease was analyzed for serum 25–(OH) D i.e. vitamin D. This was a case control study comprising of 35 patients of psoriasis and 35 normal controls. Serum vitamin D was estimated in both the groups, which showed a significant decrease in patients of psoriasis as compared to controls. Also the level seems to decrease significantly with increase in severity of psoriasis. So every psoriatic patient must be investigated for vitamin D and supplemented if found deficient or insufficient.