This Special Issue of the Cambridge Journal of Economics (CJE) marks and celebrates forty years since the publication of Keith Cowling’s (1982) seminal Monopoly Capitalism, which synthesised, updated, and extended the earlier work of scholars such as Steindl (1952), Baran and Sweezy (1966), Hymer (1970, 1972) and Kalecki (1971). Since the publication of Monopoly Capitalism, the critical transformative event has been the latest (fourth) technological revolution and the emergence of Big Tech companies such as Facebook, Apple, Amazon, Netflix and Google (aka FAANGs), alongside Microsoft and so-called ‘gig’ or ‘sharing economy’ firms (such as Uber, Airbnb). While initially regarded as exemplars of the dynamics of contemporary capitalism, in recent years there has been a public backlash against Big Tech, and its impact and influence within the global economy. Indeed, several commentators have raised concerns that beneath the veneer of Big Tech lies potentially insidious business models and practices that have led to a rise in corporate power and the monopolisation of markets. These criticisms, however, largely ignore the contributions of earlier scholars of monopoly capitalism. This Special Issue addresses this oversight with a series of papers re-examining and extending the work of Cowling and others in the monopoly capitalism tradition, in the specific context of Big Tech. The Introduction opens with a portrait of Keith Cowling, as a person and his scholarly contribution to the field. It then provides a critical assessment of the papers in this Special Issue. In the Epilogue, we summarise and conclude.