This paper reports the underlying structure of the demographic and clinical characteristics of level 3 (i.e., pathological) Korean casino gamblers. The participants reported their gambling behavior and clinical characteristics known to be associated with gambling problems (e.g., alcohol use problems, eating disorders, depression, anxiety, and impulsivity). Factor analysis identified three domains underlying level 3 gambling: emotional instability, reward sensitivity/drive, and behavioral expression. A cluster analysis identified that the "Reward sensitivity/drive" and the "Behavioral expression" were determinant factors for characterizing clusters, while the "Emotional instability" was considered as a general factor contributing to level 3 gambling. Discriminant analysis using the composite values correctly classified 95% of the participants among three clusters. These results suggest that Korean level 3 gambling is not a unidimensional disorder, but instead a multidimensional phenomenon.