Int. J. Business Information Systems, Vol. 7, No. 3, 2011 247 Copyright © 2011 Inderscience Enterprises Ltd. Inter-organisational information systems assimilation: an empirical evaluation in light of the diffusion of innovation theory Kishor Vaidya* Faculty of Information Sciences and Engineering, University of Canberra, ACT 2601 Australia E-mail: kishor.vaidya@canberra.edu.au *Corresponding author Micki Hyde Department of MIS and Decision Sciences, Eberly College of Business and Information Technology, Indiana University of Pennsylvania, Indiana, Pennsylvania 15705-1087, USA E-mail: micki.hyde@iup.edu Abstract: This paper evaluates the antecedents of public e-procurement assimilation in the context of the public sector. E-procurement assimilation attributes were identified primarily through a literature review, a research model was developed, and hypotheses were formulated. Based on the Diffusion of Innovation Theory, it was hypothesised that relative advantage and compatibility impact positively whereas complexity negatively impacts the assimilation of e-procurement. Hypotheses were tested from the data collected by means of a web-based survey of procurement/e-procurement professionals in the Australian public sector. Structural equation modelling results suggest the positive relationship between compatibility and e-procurement assimilation. While a negative relationship between complexities and e-procurement assimilation emerged as expected, only partial support was found between relative advantage and e-procurement assimilation. Keywords: inter-organisational information systems; public e-procurement; diffusion; assimilation; evaluation. Reference to this paper should be made as follows: Vaidya, K. and Hyde, M. (2011) ‘Inter-organisational information systems assimilation: an empirical evaluation in light of the diffusion of innovation theory’, Int. J. Business Information Systems, Vol. 7, No. 3, pp.247–268. Biographical notes: Kishor Vaidya is a member of faculty of Information Sciences and Engineering, University of Canberra, Australia. He received his PhD from the University of New England (Australia) and Master of Information Systems from the Central Queensland University, Australia. His current research interests include evaluation of inter-organisational information systems and public e-procurement. He has published extensively in refereed journals and international conference proceedings and is currently editing a book titled Inter-organisational Information Systems and Business Management: Theories for Researchers.