College attendance is a selective rather than a random phenomenon. Those high school students who aspire to a college education as well as those who actually enroll in college are not representative of all youths in the same age group. The greater the high school student’s intellectual abilities and aptitudes, the more likely he is to want to go to college and the more likely he is actually to attend. Self-selection on the part of students should not be viewed as involving a totally rational and fully informed consideration of well-formulated alternatives. Socioeconomic and ability selectivity operates within the institutions of a category as well as among institutions of different types. The several variables of selectivity are not of equal importance in the determination of which particular colleges students enter. Initial position of students in different schools can be taken into account somewhat more systematically.