Researchers and practitioners in several Western countries have recently developed tools for assessing the situation of the carers of adults who are ill, elderly or have disabilities. The present article describes the impact of three such assessment tools, from Canada, the UK and Sweden, on the professional practice of assessors. All tools were tested in agency-based studies. Focus groups, workshops and interviews with assessors were employed to understand the impact on professionals and their practice. An Australian researcher and case manager comments on these experiences from her unique perspective. The results reveal that the use of carer assessments can lead to changes in the appropriateness of intervention by informing practitioners of issues which are given little attention, but which impact on the adequacy of interventions to the service user. Across the projects, most workers found that the tools facilitated a more comprehensive, in-depth and carer-focused assessment. Experience across all the projects suggests that, used sensitively, such tools and approaches can play a key role in transforming the relationship between carers, and the health and social care system. Giving carers a legitimate voice, acknowledging their perspective and expertise, and making them central to assessment processes accords them status both as active partners, and as individuals with their own needs and aspirations, rather than seeing them primarily as resources. As a result of their experiences, many workers and administrators concluded that home-care programmes must change their mandate to include carers among their clients, raising the issue of available monetary and human resources to meet the needs of this group. In addition, as our Australian colleague points out, time, efficiency, relevance, benefit and minimal intrusiveness are important factors for practitioners which influence their use of assessment tools.