Due to conditions provided by the modern life, the human being is exposed to electromagnetic field (EMF). Appliance such as microwave oven, mobile phone, computer and power producing systems which have an extensive role in human life are the source of EMF. Epidemiological and experimental studies have shown the adverse effect of EMF on biological systems. Pervious works in our library using light microscopes have shown that EMF could produce morphological changes in cardiovascular system. However, there are few studies regarding ultrastructural effect of EMF on living tissues. The aim of the present study is established to investigate ultrastructural changes of heart and aorta in EMF-exposed rats for this purpose Wistar rats were exposed to 3mT EMF for 4months, 4hours/day. After the experimental period rats in all groups were sacrificed and tissue samples from heart and aorta were prepared for electron microscopic studies and TUNEL reaction technique. The ultrastructural study of Aorta showed that in experimental group there was significant decrease in the height of the endothelial cells (p0.001) in comparison controls. There was also Irregularities in the arrangement of the elastic and collagen fibers in the median layer in experimental group. The studies on the endocardium revealed that, there was destruction of subendocardial layer in experimental group. In myocardium in addition to nuclear condensation the mitochondria were also vague. There was remarkable gap between the endothelial cells and basement membrane in the vessels of heart tissue. Epicard layer in EMF exposed group was thinner than the control group.
