Information systems development (ISD) projects are becoming increasingly complex. ISD project complexity makes it difficult for project managers to deliver effective systems within time and budget constraints. As a result, the success of ISD projects is increasingly dependent on an organizationís ability to effectively assess and manage complexity. The purpose of this paper is to develop a measure for assessing ISD project complexity. A two-dimensional conceptual framework is proposed to define four distinct types of software project complexity: structural organizational complexity, structural IT complexity, dynamic organizational complexity, and dynamic IT complexity. Based on field interviews, focus group discussions, and a large-scale survey of ISD project managers, a measure of ISD project complexity with 17 indicators was developed. The results of an exploratory data analysis provide strong evidence that the final measure has satisfactory measurement properties. The contributions of this research to both theory development and practice are discussed.