This paper reports on a study examining the effects of undertaking population-based health needs assessment (HNA) on the knowledge, views and working practices of health visitors. Data were generated through indepth interviews with health visitors who had all utilized a standard mechanism for needs assessment. This was analysed to assess the impact of this work on the research respondents’ knowledge base, their attitudes and approaches to health visiting and their everyday practice. Findings suggest that undertaking health needs assessment increased understanding of public health concepts, enabled a profound reflection on current working practices and increased respondent’s desire to practise differently. However, despite these forces for change, the practitioners in this study found it very difficult to refocus their work in the way they desired due to a combination of inhibiting factors, including custom and practice and the perceptions and demands of others. If health visitors are to expand the scope of their work to incorporate an increased amount of community based activity as the UK Government is proposing, this study would suggest that these inhibiting factors must be addressed not only by health visitors themselves, but also by their employers and other primary care professionals.