Objective. To evaluate the cytoprotective effect of intravenous immunoglobulins (IVIGs) against endothelial cells. Subjects and methods. The cytotoxic effects of the sera obtained from 45 pregnant women against the endothelial cells treated with IVIGs were investigated using culture, an enzyme immunoassay, and flow cytometry. Results. After treatment of endothelial cells with IVIGs, there was a reduction in the cytotoxic effect of the sera obtained from the women with recurrent miscarriage against endothelial cells. Conclusion. IVIGs are effective cytoprotectors that are able to prevent abnormalities associated with endothelial damage and dysfunction.