This investigation prospectively predicted dropout among young soccer players, using the theory of planned behavior (TPB). First, behavioral beliefs required to develop a TPB-questionnaire were elicited from 53 male soccer players, aged 13-15 years. Second, at the beginning of the soccer season, 354 different male soccer players aged 13-15 years completed this questionnaire, thereby assessing direct dimensions (intention, attitude, subjective norm, perceived control) and indirect dimensions (attitudinal, normative and control beliefs) derived from TPB. Nine months later--upon termination of the soccer season--these players were classified into 323 perserverers and 31 dropouts, with TPB being applied prospectively to predict these two groups. For both direct and indirect dimensions, between-group comparisons revealed significant differences in favor of the perseverers. Discriminant analyses revealed five measures (intention, attitude, subjective norm, a normative belief, and a control belief), which enabled a 22.1% a priori dropout prediction when used within a suitable equation. In conclusion, TPB may have a promising application to prospectively discriminate dropouts from perseverers, providing a potential predictive a priori classification model for sport participation.