Objective To investigate the pathogenesis of the susceptibility to cardiovascular diseases in patients with psoriasis. Methods The composition of serum free fatty acid(FFA) were measured by gaschromatography in 33 patients with psoriasis vulgaris and normal individuals. Results ① Along with the increase of severity of psoriasis the levels of poly unsaturated fatty acid(PUFA) increased, mono unsaturated fatty acid (MUFA) and saturated fatty acid (SFA) decreased and PUFA/SFA ratio increased. ② The level of linoleic acid (LA) was significantly higher in the patients of progressive stage and with extensive skin lesions than that in the normal group and/or stationary stage, and the level of oleic acid decreased. ③ The changes of the composition of FFA in patients with psoriasis were diffrent from the majority of the reports studied in the patients with cardiovascular disease. Discussion and Conclusion In the severe stage of psoriasis, the metabolism of fat in the liver is accelerated; the increase of LA, which supplies enough precursor for arachidonic acid metabolism, might be related to the loss of granular layer of epidermis. The changes of FFA induced by psoriasis might be a link causing cardiovascular disease but it should be studied further.