Psoriasis is now considered to be a T cell mediated autoimmune disease in which the activated T cells produce type 1 cytokines (IL-2, IFN-gamma and TNF-alpha), which mediate complex interactions that end with the development of the psoriatic phenotype. In this study, quantitative reverse transcriptase PCR and in situ PCR hybridization methods were used to investigate the presence of IL-12 (P40) and IFN-gamma mRNA in lesional and non-lesional skin of different clinical types of psoriasis as well as in normal controls. IL-12 and IFN-gamma levels in lesional skin were higher than in non-lesional and control skin (P value < 0.001). Clinical types of psoriasis, PASI score, patients’ age, sex, and predisposing factors did not affect the expression of these two cytokines. A good significant correlation between IL-12 and IFN was found when lesional and non-lesional skin values were considered (r value = 0.656, P value < 0.001). IL-12 levels were not correlated with disease duration both in lesional and non-lesional skin, while IFN levels only in non-lesional skin were inversely correlated with disease duration (r value= -0.376, P value= 0.040). By using In situ PCR hybridization, IL-12 expression was only found in the dermis, while IFN-gamma was invariably expressed in dermis and/ or epidermis.Results of the present study indicate that IL-12 has a role in psoriasis and confirm the role of IFN-gamma in the development of the disease, irrespective of the clinical type or severity