Changes of intracellular calcium homeostasis in epithelial cell damage of renal tubules caused by cadmium and its relationship with the damage were studied in isolated tubular cells of rabbits. Results showed levels of free calcium (Ca++) in tubular cytoplasm increased significantly with the treatment of cadmium, and a series of cellular ultrastructure were damaged. A calcium channel blocker, phenothiazine, showed blocking and protecting effects on it. This suggested calcium overload played a very important role in kidney damage caused by cadmium.