Objective: To assess the potential involvement of the soluble endothelial cell-leukocyte adhesion molecules E-selectin and intercellular adhesion molecule-1 (ICAM-1) in the pathophysiology of capillary hyperpermeability in the ovarian hyperstimulation syndrome (OHSS). Design: Controlled clinical study. Setting: Women hospitalized for severe OHSS after ovulation induction for IVF at two tertiary medical centers. Patient(s): Eleven patients with severe OHSS undergoing IVF and 20 controls who had received a similar ovulation induction regimen and did not develop OHSS. Intervention(s): Serial serum samples were obtained from all patients with OHSS from admission until discharge. Ascitic fluid was obtained from all patients by therapeutic paracentesis. Serum was obtained from all controls 4–8 days after ET. Main Outcome Measure(s): Samples were assayed for soluble E-selectin and soluble ICAM-1 by using enzyme-linked immunosorbent assay and results were correlated with clinical and biological aspects of OHSS. Result(s): Compared with controls, patients with severe OHSS had higher levels of soluble ICAM-1 and lower levels of soluble E-selectin detected in serum and ascites. Serum levels of soluble ICAM-1 decreased, while soluble E-selectin levels increased along with clinical and biological improvement. Serum soluble ICAM-1 showed significant positive correlation and serum soluble E-selectin showed significant negative correlation with clinical and biological aspects of severe OHSS. Conclusion(s): Soluble ICAM-1 and soluble E-selectin seem to be involved in the pathophysiology of capillary hyperpermeability in severe OHSS.