The investigation was carried out by using psychological, not traditional anatomical and biomechanical methods. Therefore new data were obtained for further examination of working comfort. Two motor areas were studied: “comfortable” and “discomfortable”. The study involved the performance of rapid and exact movements in the above motor areas. The subjects were tested in sitting and standing postures until they were sensible to fatigue and pain in some parts of the body. The changes in the accuracy of movements in the course of certain time, as well as the subjective judgements on fatigue and pain were measured. The analysis of the data showed that the motor space comfort and the posture were not the·only factors relevant to the efficiency of the movements. Correlations were found between the person's temper and the changes in the efficiency of movements in the course of certain time. The fatigue time also depends on the personality. In this paper diagrams are presented in which the fatigue time and the efficiency of rapid, exact hand movements has been shown.