An instrumental theory of development of occupational interests is presented. The interests are represented in it as a dynamic combination of selective cognitive, emotional, and volitional activities. A genetical structure of the interests is suggested which encompases all stages starting from that of birth till maturity. Some psychological mechanisms of control over the development of occupational interests have been established. The theory is based on critical analysis of both domestic and foreign literature; it has been checked in the author's experiments with representatives of different populations (preschool children, pupils of general education schools, students of high schools, teachers, workers in mass professions).