There has been a growing interest in the application of biorhythm theory to programmes of accident prevention and performance prediction. In order for biorhythm to be applie to practice its validity and reliability should be established. This paper reported the results of three different set of data, and these data were tabulated and analysed in various ways. The basic method of analysis consisted of stat- istical comparision of actual frequences of occurrence from the collected data with those frequencies which would be expected if biorhythm had no effect. The results of the occurrence data indicated that no definite evidence in support of the influence of the fundamentals could be detected. Actual frequencies of occurrence from the collected data were not significantly different them those expected assuming random occurrence.