Psoriasis is a common chronic, recurrent, immune mediated disease of the skin and joints. It can have a significant negative impact on the physical, emotional, and, psychosocial wellbeing of affected patients. Psoriasis is found worldwide but the prevalence varies among different ethnic groups. It has a strong genetic component but environmental factors such as infections can play an important role in the presentation of disease. There are several clinical cutaneous manifestations of psoriasis but most commonly the disease presents as chronic, symmetrical, erythematous, scaling papules and plaques. Methotrexate (MTX) has remained the backbone of the treatment for moderate to severe psoriasis ever since its first use nearly half a century ago. Over the years, its high efficacy, low cost, relative ease of administration and usefulness in concomitant psoriatic arthritis have contributed in making MTX the drug of choice in managing severe psoriasis. Although the majority of patients achieve remission of disease activity with MTX, a significant proportion may experience mild and transient adverse effects.  In this study, it was aimed to evaluate the factors which affecting response to psoriasis treatment. The study included 28 patients suffering from psoriasis and 30 healthy control subjects of different age, sex, disease duration and PASI score.