The telephone is one of the most widely used technologies in the advanced industrial economies, typically achieving a household penetration rate in excess of 90%. Over the course of this century, the plain old telephone system (POTS) has become a critical techno-social infrastructure for all sorts of economic, social and personal interactions. The question arises as to what has driven the widespread diffusion of the telephone? How can we describe the adoption of telephony as a core element in economic and social affairs in modern societies? In particular, how can we account for the great disparities in the rate and pace of the diffusion patterns of POTS, taking account of different national and historical contexts? This paper critically interrogates influential universal models or 'theory-led' explanations of the diffusion of telephone systems, especially their capacity to account for the empirically observable national variations. The authors test these models with respect to the historical trajectory of telecommunications development in Ireland, drawing on unique time-series data related to the actual patterns of telephone adoption, use and utility. The authors also re-assess the extent to which existing diffusion models throw some light on aspects of observable diffusion processes and patterns. A key conclusion from the approach adopted here is that in themselves, abstract deductive models are at best unsatisfactory. Whilst a combination of such 'universal' factors derived from more deductive models may be useful in elucidating different parts of the story, they are not sufficiently nuanced or adequate to describe or frame the complex stories of different national historical experiences. With the Irish case study we have attempted to illustrate the value of a historical and empirically based understanding of the socio-economic, political or institutional factors which have served to shape the development of telecommunications services and policy in Ireland. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.