The purpose of this study was to measure the serum level of sICAM-1 and sE-selectin as markers for endothelial damage in patients with dengue fever (DF) and dengue hemorrhagic fever (DHF). Twenty-nine patients with serologically-proven dengue virus infection (age 10.6 +/- 2.4 years, 55% male, DF = 13 and DHF = 16) were enrolled. Serum samples were collected from 25 healthy children (age 10.6 +/- 2.3 years, 40% male) as the control group. A follow-up was done at a mean interval of 15.9 +/- 1.6 days. The level of sICAM-1 at the toxic stage was significantly elevated compared to its level at the follow-up (494.1 +/- 107.4 versus 358.2 +/- 67.6 ng/ml, P = 0.001), but no difference was found between patients with DF and patients with DHF (444.1 +/- 158.0 versus 465.1 +/- 154.6 ng/ml, P = 0.74). The sICAM-1 level at the follow-up was similar to that of the control group (396.9 +/- 113.0 ng/ml, P = 0.56). The level of sE-selectin at the toxic stage was not different from its level at the follow-up (75.9 +/- 33.0 versus 75.5 +/- 31.7 ng/ml, P = 0.96), and no difference was found between the DF group and the DHF group (64.1 +/- 25.7 versus 78.8 +/- 39.9 ng/ml, P = 0.30). These levels were not elevated compared to the sE-selectin level that was determined in 8 patients in the control group (94.7 +/- 20.5 ng/ml, P = 0.12). In conclusion, there is evidence of endothelial activation by an increased sICAM-1 level in patients with dengue virus infection. However, the degree of endothelial activation alone may be similar for patients with DF and patients with DHF, and this fact by itself cannot explain the difference between the two clinical syndromes of dengue virus infection. The sE-selectin level was not elevated for patients included in this study.