To investigate the mechanism of the occurrence of peripheral circulatory disturbances in the Hand-Arm Vibration Syndrome, serum Ca and Mg in workers using vibrating tools were measured. Serum Mg levels in workers with Raynaud's phenomenon were significantly lower than those in workers with no symptoms. Serum Ca/Mg in workers with Raynaud's phenomenon was slightly higher than that in workers with no symptoms. Fingertip skin temperature, which is the index of peripheral circulatory disturbances, in workers with Raynaud's phenomenon was slightly lower than that in workers with no symptoms. These results suggest that there are some relationships between the decrease of serum Mg and the increase of serum Ca/Mg, and the occurrence of peripheral circulatory disturbances in the Hand-Arm Vibration Syndrome.