Studies(Ginzberg, Lindahl, Lipsett) indicate that there are certain stages in development of vocational goal in individual, and intellectual and socio-economic status affect one's selection of a vocation. The purpose of this study was to examine the extent of vocational understanding and variables influenced to development of vocational understanding and selection of future vocation in our secondary school students. A questionnaire was administered to 1,400 subjects randomly selected from four junior and four senior high schools of both sexes. In addition to the administration of the questionnaire, an intelligence test was given to all subjects, and information concerning subjects' family back ground was also collected. The subjects were divided into three IQ levels with equal number of subjects at each IQ level. Subjects' family background was converted to numerical value using a scale developed by Young-me Kim, and the subjects were divided into four socio-economic levels of equal number according to the numerical value assinged to each individual. Responses of subjects were compared between these levels of intelligence and socio-economic status. As the results, the followings were found; As age levels increased, subjects' concern for their future vocation was increased. The incre ment, however, was unexpectedly small showing that only 18% of boys and 15% of grils of 12th graders have decision on their future vocation. Girls in general showed significantly lower concern in their future vocation than boys of their age level. Boys had higher vocational ambition than girls of their age level. There were no significant differences between higher and lower groups of intellectual levels in their vocational ambitions as well as in maturity levels of vocational concern. There were no significant differences between higher and lower groups of socio-economic levels in their vocational ambitions as well as in their maturity levels of vocational concern. There was no significant difference. in expectation of success in their future vocation between higher and lower groups of intelligence. Boys from higher socio-economic background showed higher expectation of success in their future vocation. Boys consider, in selecting their future vocation, the value of a vocation, interest, ability, pay, and parents' expectations in order, while the order of cosideration for girls was value, ability, interest, parents, expectations, and pay.