The purpose of this study was to examine the relationship between length of time as a fan, motives to attend games, and involvement with the J. League (Japan Professional Soccer League). Data were collected using a self-administered questionnaire during J. League games at five stadiums in 1997. Using proportionate sampling methods stratified by gender and age, researchers collected a total of 2,843 responses. Spectators were then categorized into three segments according to J. League attendance trends. This study suggests that length of time as a fan, which demonstrates valid correspondence to both spectators' motivation and involvement, represents a useful independent variable for creating marketing segments. The paper discusses the utility of different strategies for each segment. In particular, the current study examined the potential usefulness of supporter clubs in future marketing strategies. Finally, the potential application of the strategies suggested for the J. League to other new sport leagues was explored.