Plasma nitrite/nitrate levels in patients with psoriasis. Psoriasis is a chronic inflammatory skin disease characterised by increased keratinocyte proliferation, hyperkeratinisation, leu¬cocyte hemotaxis, and neoangiogenesis. During the different phases of the disease, many of the cytokines and other inflammatory mediators derived from inflammatory cells, including macrophage and T-lymphocytes, are released. It was found that some of these cytokines incre¬ase NOS expression in human keratinocytes, thereby increase nitric oxide levels in circulation. Increased nitric oxide levels may have role in formation of inflammatory lesions, hyperkerati¬nisation, and neoangiogenesis (the main characteristics of psoriasis). Plasma nitrite/nitrate le¬vels of 30 patients with psoriasis were compared with those of 20 healthy subjects. Mean plas¬ma nitric oxide levels in psoriatic patients (73.9± 23.7 (mol/L) were higher than these in cont¬rols (50.76 ± 14.37 umol/L) (p<0.001). There was a significant correlation between nitric oxi¬de levels and impaired body area (r=0.68; p<0.05). We concluded that increased nitrite/nitrate levels probably are important in clarification of etiopathogenesis of psoriasis.