Abstract: The biorhythm theory is a new viewpoint about the causes of human behavior.It assumes that everything human beings do is influenced by a 23-day physical cycle, a 28-day emotional or sensitivity cycle and a 33-day intellectual cycle. This paper deals with whether any correlation exists between motor vehicle accident and biorhythmic stales of the driver wor not. 490 motor vehicle accidents being at fault with the driver were analysed. The author thinks that the important work for improving traffic safety should place on the driver's performances. In this paper some experimental study was examined. It was reported that when the driver's critical days were impending, the manager issued warnings to them according to their biorhythm charts or tables, then the motor vehicale accidents were reduced. In future it is necessary to research biorhythms with adequate "control group", and take into account the environmental effects.