Psoriasis is an common, chronic, recurrent, inflammatory disease of the skin, characterized by red scaling plaques on the skin surface. The morphology of psoriatic lesions allows classification of the different types of psoriasis that included plaque type, pustular type and Erythrodermic type. I have studied the relationship between distribution of RH and ABO blood groups in 110 psoriatic patients and compared with control normal blood groups. The result of this study was as follow: The rate of blood group type AB was significantly lower than that of the control normal blood group ABO