This paper presents a model, based on organizational design literature, of the impact of Enterprise Resource Planning (ERP) software on operational effectiveness. Convergent, discriminant, and predictive validity of the model's proposed constructs are evaluated using a dataset gathered from implementers of ERP systems via a survey instrument. To address the problems inherent in single-respondent survey research, multiple respondents were solicited from each participating organization. This research finds support for all three types of validity at the level of the implementation, although convergent and discriminant validity are generally not demonstrated when individual responses within each implementation are compared.