Background: Controversial data concerning the elevation of serum angiotensin-converting enzyme in psoriasis are reported in the literature. In order to verify whether this abnormality exists in Iranian patients, we performed this study. Method: Serum angiotensin-converting enzyme level was measured in 40 psoriatics. According to clinical forms of psoriasis, patients were further divided into three groups: common plaque type (n=24), pustular psoriasis (n=10) and erythrodermic psoriasis (n=6). Results: Serum angiotensin-converting enzyme shows some increase in patients with psoriasis; the greatest increase in serum angiotensinconverting enzyme level was observed in patients with erythrodermic psoriasis. Conclusion: Our results suggest that angiotensin-converting enzyme may have a role in the aetiopathogenesis of psoriasis but further studies are warranted to evaluate the possible role of this enzyme in psoriasis.