The overuse of Massively Multiplayer Online Role Playing Games (MMORPGs) is becoming a significant problem worldwide, especially among college students. Similar to Internet addiction, the pathological use of MMORPG is a kind of modern addiction that can affect students' lives on both a physical and a psychological level. The purpose of this study is to understand MMORPG addiction from a user experience design approach. We first developed a complete model that includes eleven factors ("challenge," "fantasy," "curiosity," "control," "reward," "cooperation," "competition," "recognition," "belonging," "obligation" and "role-playing") to represent users' experience in MMORPGs. After that, we design a questionnaire to measure students' gaming experience and level of addiction. Students' demography information, including gender and game playing habits, was also collected. Four hundred and eighteen Taiwanese college students aged 18-25 years old took part in this online survey. Regression analysis was then conducted to evaluate the relative explanatory power of each variable, with addiction score as the dependent variable and the eleven user experience factors as the independent variables. The results of regression analysis reveal five critical factors (curiosity, role-playing, belonging, obligation and reward) that can be used to predict MMORPG addiction. In addition, this study also infers possible casual mechanisms for increasing college students' level of addiction. The implications of our findings for both design and educational practitioners were also discussed. (Contains 1 table and 2 figures.)