This study of gender differences in the sport socialization process of high school varsity athletes examined: (1) the primary and secondary patterns of sport involvement by significant others; and (2) the primary sources of motivation for athletes' entrance into sport and continued sport involvement. A 96-item Sport Participation Inventory was administered to 119 male and 75 female varsity athletes representing 12 varsity sports. Results revealed that: (1) more females than males reported that their sisters participated in sports and were sport fans; (2) more males than females reported that their friends frequently participated in recreational physical activities during childhood and that their parents provided the most motivation to begin participation in sport; (3) females reported that they were primarily self-motivated in sport participation; and (4) both males and females reported that they were primarily self-motivated to continue sport participation. There were no gender differences in the sources of motivation for continued sport involvement. (JD)