This paper presents findings from a qualitative study of social isolation in the context of service provision to older people. It draws on in-depth interviews with 18 Australian aged care practitioners about their perceptions of social isolation among their clients. The findings show that service providers experience significant levels of concern and frustration and a sense of powerlessness in meeting the needs of such clients. In analysing these accounts, the identification and management of isolation is conceptualised as a social practice which occurs in specific relational settings. The provision of care to lonely, isolated old people is structurally constrained in two ways. First, because of inadequate public resource allocation, the relationship between practitioners and older clients is dominated by time pressure and instrumentality. Secondly, the organisational and professional rules which service providers are required to follow shape the interpersonal relations between practitioner and client in ways which negatively impact on the outcomes of care for both.