This paper presents a quantification of the macroeconomic and sectoral economic implications of the adoption of Information Society Technology (IST) in Western Europe. The work implements key IST effects using the Cambridge Econometrics dynamic macroeconomic model E3ME, through the design, implementation and analysis of four IST scenarios. The key effects modelled are based on the results of research in the rest of the SEAMATE project (the European Commission DG Information Society project Socio-Economic Analysis and Macro-modelling of Adapting to Information Technologies in Europe (BIBA, 2003; Cambridge Econometrics, 2003a, 2003b; Econcept, 2003; ISIS, 2003; SINTEF, 2003) and cover success in European IST investment, the implementation of e-business in key sectors, the economic consequences of the digital divide, and the consequences of widespread adoption of e-banking. The work aims to place the scale and significance of IST in the context of the general path of economic development and the policy goals to which it is hoped that wider adoption of IST will contribute.