Collaboration between hospitals and community organisations has been promoted over the past 20 years by various levels of government, hospital associations, health promotion advocates, and others at the state/province, national and international levels as a way to improve the 'efficiency of the system', reduce duplication, enhance effectiveness and service coordination, improve continuity of care, and enhance community capacity to address complex issues. Nevertheless, and despite a growing literature on interagency collaboration, systematic documentation and empirical analysis of hospital-community collaboration (HCC) is almost completely lacking in the literature, particularly as regards collaborations that address the determinants of health beyond the hospital walls. In this paper, we describe the methodology and key findings from a research study of HCC. The Hospital Involvement in Community Action (HICA) study undertook detailed qualitative case studies (in four urban, suburban, rural and northern locations) and a telephone survey (of 139 community organisations in a large urban centre) in order to learn about the range of collaborations and working relationships that exist between hospitals and community agencies in the province of Ontario (Canada), and the factors that influenced (enabled and/or hindered) HCC. Particular attention was paid to barriers and enablers at three nested levels of context (policy, hospital and community) and, drawing primarily on the qualitative case studies, it is this aspect that is the focus of this paper. That such collaborations continue to be widespread despite a generally unfavourable policy environment and hospital institutional culture that poses significant barriers, suggests that the extent to which HCC flourishes (or exists at all) crucially depends on the presence and ongoing enthusiasm/commitment of one or more 'champions' within the hospital, and the commitment of both parties to overcome the marked cultural differences between hospital and community. We conclude with a discussion of implications for policy and practice.