Pathological gambling is a serious social issue, but the underlying psychological motivations are poorly understood. This study developed a five-factor gambling motivation model. The five factors that motivate gambling (socialization, amusement, avoidance, excitement, and monetary motives) were derived from study data obtained from 240 college students. The structure of the five-factor model was confirmed by factor analysis of responses from 234 frequent gamblers. We then compared the "monetary motive version" of this model with the "parallel version" to determine which model more accurately describes how the five factors influence gambling. The monetary motive model holds that amusement, excitement, and avoidance motives influence gambling severity only through mediation of the monetary motive. The parallel model proposes that the five motives all independently influence gambling severity. We found that the avoidance and excitement motives did not have direct effects on gambling severity, but the monetary motive showed a direct positive influence. Thus the monetary motive model was more effective than the parallel model in explaining the influence of specific gambling motives on gambling severity. These findings may help in the improvement of therapy for pathological gambling.