The ageing process was studied by means of the changes in the aptitude measured by the general vocational aptitude test constructed by the Japan Labour Ministry. The aptitudes were classified in terms of three activities, viz. analytical, synthetic and motion. Four groups of subjects participated in the study: 271 male manual workers aged 20-59; 111 male non-manual workers aged 20-59; 196 male and female university students aged 18-19; and 123 male and female junior high school students aged 13-15. Changes with age were observed in the scores, in the activity balance diagram and in the time required for the basic motion (therblig).