Follow-up data were gathered on 4,272 male physicians, twelve years after they were administered the Myers-Briggs Type Indicator, as first-year medical students. The indices included sensation/intuition; thinking/feeling; extrovert-environment/ introvert-ideas; and judging/perception. The identity of the dominant process was deduced from all four indices conjointly. Results indicated that high school graduates with the following characteristics were most likely to go to medical school: introversion, intuition, feeling, and perception. Persons with all four characteristics were at least four times as likely to go to medical school as classmates with the opposite four characteristics (extroversion, sensation, thinking, and judging), which were associated with business professions. Dropout rate was related to whether the predominant process was perception or judging, a combination of extroversion/introversion and judging/perception conjointly. The Myers-Briggs indicators were also predictive of type of specialty chosen; the indicators were more predictive than intelligence. It was suggested that, in vocational choice, people like to use their preferred types of perception and judgment, and tend to choose occupations that give them that opportunity. Paper presented at APA, Los Angeles, September 1964.