Abstract : Abstract: Background: psoriasis is a multifactorial disease, where the genetic predisposition has a big role in the disease development. Rationale: few studies try to prove that null GSTM1 and GSTT1 associated with psoriasis development. Aim: to evaluate the role of null GSTM1 and GSTT1 on psoriasis development as a genetic risk factor. Material and method: diagnostic case-control study evaluate the availability and the role of polymorphic genotyping of GTMS1 & GTTS1in development of psoriasis, done in Thi-Qar University research unites , extended all-over the 2017. Equal number of well crossly matched psoriatic patients and control (100) of each group. Family history, smoking status , stressful event assessment and co-infection had been assessed well. Ethical consideration had been optimally taken from the ethical committee, ethical approval accomplished by verbal consents from all participants, P value < 0.05 consider as significant comparative cut. GSTT1, GSTM1and albumin genes had fully assessed by fully automated PCR, Deletion occurring when only albumin gene present without GSTM1or GSTT1. Result: among psoriatic patient the value of genotypes of GSTM1, GSTT1 and combined was present in a percent of (37,66 and 27%) while in control group (51,80 and 40%), that show significant difference, and role of protection was obvious, where the strength of association that expressed by odd's ratios that were less than one in all state of comparison.