Cardiac cell was cultured in low (5%) and normal (20%) bovine serum medium with or without molybdenum (Mo) supplementation (0.7ppm). Spontaneous contraction of the cultured cells was examined periodically. It was observed that the spontaneous contraction of the cardiac cells cultured in the low serum medium was better than that in the same medium without Mo and the frequency of the contraction was almost near the one cultured in normal serum medium. Some strengthen effect of Mo on the contraction was also seen in cardiac cell cultured in the normal serum medium with Mo.It suggested that Mo was necessitated in the contraction of cardiac cell and might be involved with the pathogenesis of certain cardiac diseases and Keshan disease and with their prophylaxis and treatment as well.