Strategic alignment between business and IT is known to be important for achieving good business performance in one organization. It is not clear how strategic alignment influences the performance of networks consisting of multiple organizations. This paper presents a method to assess inter-organizational Extended Strategic Alignment (ESA) based on the analysis of inter-organizational alignment processes consisting of drivers, levers, and impacts. The method has been applied to a large e-government network for social security in the Netherlands. In this paper we propose to use the Extended Strategic Alignment method to assess the impact of IT on organizational and network performance in health care. The paper is work in progress: we have finished one large case study in social security on the national level. Two other cases on health care networks (the ‘payment services network of the national dentist association’ and the ‘the national electronic locum record for general practitioners’) are in progress.