Three studies tested relations between self-related constructs and approach and avoidance achievement goals in a health-related physical activity context. Physical self-concept was hypothesized to be positively related, and social physique anxiety to be negatively related, to approach goals in physical activity. Achievement goals were also expected to mediate relations between the self-related constructs and behavior. Structural equation models supported the hypothesized pattern of effects in a physical activity context (Study 1). The model for physical activity was invariant across collectivistic and individualistic cultures (Study 2). Relations between physical self-concept, social physique anxiety, and achievement goals were stronger among regular gym and fitness center users than among nonusers (Study 3). The findings are discussed in relation to achievement goal theory.