Despite the enormous groundswell of interest in partnering and alliancing in recent years, there has been comparatively little research that has set out to investigate systematically the nature, feasibility, benefits and limitations of forms of client-contractor collaboration. This is despite the growing recognition that conditions conducive to partnering may well vary considerably and that partnering may not be the solution for problems within the industry that many commentators have taken it to be. This paper sets out to add to the growing literature and empirical database on partnering by reporting the findings of a research project designed to explore the economic, organizational and technological factors that encourage or inhibit collaboration in practice. The paper follows on from an earlier review and critique of the literature on partnering (Bresnen, M. and Marshall, N. 2000, Construction Management and Economics, 18 (2) 229-37). It includes as its database nine case studies of medium-to-large-scale projects, selected from across the industry, on which processes of collaboration are examined from the viewpoints of clients, contractors, designers and subcontractors. In contrast to much of the prescriptive work in this area, the analysis of the data and the paper's conclusions stress some of the practical problems, limitations and paradoxes of partnering and alliancing when the effects of important economic, organizational and psychological factors are taken into account.