Aging populations present serious challenges to societies for the provision of care and support for their eldest members. These include increased demands on families for care at home, shortages of professional care workers and facilities, and financial strains on governmental budgets. However, these conditions also provide space for the elderly to adapt institutions to secure care and support. This essay examines the ways the elderly work through Min-Iren, a federation of medical institutions in Japan, to meet their needs. Premised on a "democratic" model of solidarity, Min-Iren institutional structure provides participating elderly substantial power to modify ostensibly medical institutions. Drawing from 18 months of fieldwork, this essay ethnographically explores how the elderly refashion Min-Iren clinics and hospitals to offer venues for socializing, community building, and political action as well as conventional medical care. On the medical side, Min-Iren institutions enact a form of coproduction of health. However, interpreted from the perspective of social capital, Min-Iren institutions' forays into local social milieus resemble activities of civic organizations and foster social engagement, collective action, and social support. In the hands of the elderly, Min-Iren medical institutions, thus, endeavor to improve individual and neighborhood wellbeing in ways beyond medical care. Min-Iren's model that centers participation and local ownership is general and can be applied to other contexts.