Identifying the best way to organize the IS functions within an interprise has been a critical IS management issue since the mid-1980s. Yet to date, MIS researchers have offered little empirical evidence on which to base guidelines for the practitioner. This study seeks to explain a firm's IS organization design decision for a decentralized, centralized, or "hybrid" locus of responsibility from an expanded set of environmental, overall organizational, and IS-specific antecedents as well as a larger concept of organizational alignment. Potential antecedents (drivers or enablers) are selected from prior contingency research and the IS literature; other variables emerge from the data collection. Data collected via on-site interviews from IS and general managers in six multi-divisional firms, paired by industry, confirm that centralized, decentralized, and hybrid IS structures exist-but often not in "pure" form-and that industry type is not a strong predictor. Data was also collected via survey form to capture ratings of importance for drivers (for enablers) for a recent IS design change in each firm. Based on both qualitative and quantitative data, four configurations are discussed: patterns of antecedents that are associated with (1) highly centralized or (2) highly decentralized IS structures; and patterns of antecedents that explain a firm's choice to (3) decentralize or (4) recentralize systems development and application planning functions in particular. A model based on these configurations is then proposed. The article concludes with implications for researchers and practitioners.