This study investigated the effects of participation in a Japanese-American youth basketball league on the assimilation of its members into the dominant American culture. Two groups of Japanese-Americans were compared: participants (players) and non-participants (non- members). The data were collected by a written questionnaire, formal and informal interviews, and direct observation. Significant differences at the .05 level were found between the groups in the dimensions of structural, marital and identificational assimilation. Participation in the ethnic basketball league did not appear to promote overall assimilation into the mainstream of American life. Instead, it seemed to reflect an index of ethnic solidarity for Japanese-Americans.