Objectives: To examine the use of knowledge, and in particular, of evidence derived from research, in interactions between community midwives or health visitors and their clients around the topic of breastfeeding. Design: A qualitative study involving observation of practice (n = 158) and in-depth interviews with women (n = 22), midwives (n = 9) and health visitors (n = 9). This paper draws primarily on interviews with health professionals. Setting: Inner city, suburban and rural areas of a northern city in England. Findings: A range of different sources of knowledge were used, including: clinical experience; training courses; reading journals; research, policies and guidelines; watching or speaking to colleagues; and personal experience. Practitioners considered each woman's individual circumstances, drew on their knowledge of what had worked with other women and used knowledge from formal and informal sources, in an ongoing process of feedback. This accumulation of previous experiences acted as a reference point to test out new information including research findings. The process of building knowledge over time from different sources, formal and informal, seemed to lead to practices that generally concurred with current research evidence. The potential strengths and weaknesses of this approach are discussed, and implications for practice and research are described.