Abstract: ObjectiveTo investigate the effects of high power microwave radiation on ultrastructure of parenchymal cell of heart and liver in rats.MethodsThirty six adult Wistar rats(halfmale and half female)were randomly divided into normal control and microwave radiation group with eighteen rats in each group.The rats in microwave radiation group were exposed to 100mW/cm² in tensity microwave radiation for 6 min.The rats in each group were killed at 1,7 and 14 days after the exposure.The heart apex fresh tissue and right leaf liver tissue were taken immediately underice bath,and prepared to routine transmission electron microscopy specimen.The pathological changes of the cells were observed with transmission electron microscopy.ResultsOne and seven days after the microwave radiation,some changes of ultrastructure in myocardium and liver of the rats were observed,such as the heartm itochondria(Mit)swelling,vacuo lization,myofilament dissolution.Fracture and nucleus hetero chromatin increased and some mitochondria cristae blurred.The rough endoplasmic reticulum of liver cells were irregularly arranged one day after the exposure and pathological changes of Mit were observed seven days after the exposure.Fourteen days after the microwave radiation,pathological changes of Mit were not apparent.The part of myofilament dissolution and fracture,lipid droplets within the cytoplasm and inflammatory cell infiltration in several liver cells were observed 14 days after the microwave radiation.ConclusionDifferent degrees of damage on parenchymal cells of heart and liver induced by high power microwave radiation were observed in rats.Heart and liver are sensitivie to high power microwave radiation.Ultrastruc tural changes of myocardial cell in jury induced by high power microwave radiation is more severe than that of hepatocytes,and the time of repair ofmyocardial cell injury is longer than that of hepa to cyte injury.