A limitation of most prior research concerning socialization via sport has been a reliance on cross-sectional/correlational designs. Thus, one purpose of the study was to overcome this limitation by implementing a longitudinal design. A second purpose was to test the efficiency of two theories—self-selection and interaction—that attempt to explain value, attitudinal, and/or behavioral differences often noted between elite and casual athletes, and between athletes and nonathletes. Instructional and competitive league soccer players were interviewed before and after their seasons to ascertain changes in their sport-related value orientations; this procedure was repeated the following season with the competitive league players. The data for the subsamples revealed (a) some initial differences in value orientations, and (b) a slight modification of values during participation over the course of a season. The implications of the findings are discussed in terms of the study’s purposes, future research, and their meaning for youth sport practitioners.