Effective measurement of the enjoyment of computer game play will assist game designers to understand the strength and flaw of the game from players’ perspective. We argue that flow experience in computer game play contributes to enjoyment. This paper reports on the development of an instrument for measuring flow experience in computer game play. The instrument was developed based on the flow theory (Csikszentmihalyi, 1993) and a rigorous method introduced by Moore and Benbasat (1991). The results show that the validity and reliability of the instrument are satisfactory. This instrument will help IS researchers to further investigate the application of flow theory in computer games.