The aim of the study was to determine the plasma level of sICAM-1 in acute psoriatic patients in contrast to normal subjects. Moreover, we have tried to answer whether disease severity index (PASI) correlates with plasma level of sICAM-1. We have determined the plasma levels of sICAM-1 by ELISA (Genzyme Corporation) in 23 patients with acute psoriasis before and after the treatment of the disease and in 11 controls. Patients with acute psoriasis have displayed higher levels of sICAM-1 (306.4 +/- 226.8 ng/ml) compared with the controls (141.2 +/- 49.2 ng/ml) and the same patients after clearing of the disease (154.7 +/- 126.7 ng/ml). We have not found any correlation between plasma levels of sICAM-1 and severity index of psoriasis (PASI). We have concluded: the plasma levels of sICAM-1 are not related to disease severity in acute psoriasis. Clearing of the psoriasis is followed by significant fall of plasma sICAM-1.