The objective of this study is to determine the association between maternal cigarette smoking and the subendothelial content of fibronectin and collagen type IV. Ten pregnant women using five or more cigarettes per day comprised the study group and ten healthy pregnant women with normal pregnancy comprised the control group. Quantitative (the thickness of the subendothelial layer containing fibronectin and collagen type IV positive extracellular matrix) and qualitative (the pattern of distribution) subendothelial alterations of collagen type IV and fibronectin distribution in the subendothelial region of umbilical arteries and veins of the two groups were investigated by immunohistochemical staining. Student's t- test was used to compare the means of quantitative data. Fibronectin content of umbilical vein in the control group was found to be significantly lower than the study group (p=O.O26). Collagen type IV content of umbilical vein in the control group was found to be significantly higher than in the study group (p=O.OOO). We concluded that subendothelial collagen type IV and fibronectin content is altered in smoking mothers resulting In adverse effects upon the placental vasculature.