Across the United Kingdom, large numbers of crisis resolution and home treatment services have been established with the aim of providing intensive, short-term care to people who would otherwise be admitted to mental health hospital. Despite their widespread appearance, little is known about how crisis resolution and home treatment services are organised or how crisis work is done. This article arises from a larger ethnographic study (in which 34 interviews were conducted with practitioners, managers and service users) designed to generate data in these and related areas. Underpinned by systems thinking and sociological theories of the division of labour, the article examines the workplace contributions of mental health professionals and support staff. In a fast-moving environment, the work which was done, how and by whom, reflected wider professional jurisdictions and a recognisable patterning by organisational forces. System characteristics including variable shift-by-shift team composition and requirements to undertake assessments of new referrals while simultaneously providing home treatment shaped the work of some, but not all, professionals. Implications of these findings for larger systems of work are considered.