Collagen IV is the main collagenous component localized in the trophoblast and glomemlar basement membrane. Serum collagen V reflects degradation of basement membrane collagen. In this study, we measured collagen IV levels in maternal serum, umbilical cord serum and amniotic fluid, both from preeclamptic and normal pregnant women, by radioimmunoassay. The serum collagen IV levels in the preeclamptic group were significantly (p < 0.05) higher than those in the normal pregnant group. The amniotic fluid collagen IV level at term was found to be higher than maternal serum collagen IV. We postulate that collagen IV may have an important role in the maintenance of pregnancy. There was a significant positive correlation between maternal serum collagen IV levels and serum laminin levels. There was no significant correlation between maternal serum collagen IV level and blood pressure, urinary protein concentration, or any other laboratory data. These results suggest that there is early damage of endothelial cells in preeclampsia.