Commitment to an information systems (IS) development project is widely believed to affect the eventual success of the system. Problems arising from low commitment have also been described. However, there has been little research on the factors that influence the level of commitment to an IS project. This paper provides some initial insights into the determinants of commitment based on a longitudinal study of an IS project that was stopped and then restarted on several occasions over a 17-year period (1975-1992). The paper draws four types of determinants -- project, psychological, social, and structural -- from the organization behavior literature and uses them to explain six decisions that were made during the 17-year period. A comparison of these six decisions suggests that project determinants play a central role during the initial commitment decision, but the other determinants assume greater importance in later stages. Moreover, it seems that in this case study, project and psychological determinants affected the decision to increase commitment, whereas social and structural determinants influenced the decision to withdraw commitment to the project. Some implications for practice and future research are examined.