BACKGROUND: Intermittent preventive treatment of malaria in infants (IPTi) reduces the incidence of clinical malaria. However, before making decisions about implementation, it is essential to ensure that IPTi is acceptable, that it does not adversely affect attitudes to immunization or existing health seeking behaviour. This paper reports on the reception of IPTi during the first implementation study of IPTi in southern Tanzania. METHODS: Data were collected through in-depth interviews, focus group discussions and participant observation carried out by a central team of social scientists and a network of key informants/interviewers who resided permanently in the study sites. RESULTS: IPTi was generally acceptable. This was related to routinization of immunization and resonance with traditional practices. Promoting "health" was considered more important than preventing specific diseases. Many women thought that immunization was obligatory and that health staff might be unwilling to assist in the future if they were non-adherent. Weighing and socialising were important reasons for clinic attendance. Non-adherence was due largely to practical, social and structural factors, many of which could be overcome. Reasons for non-adherence were sometimes interlinked. Health staff and "road to child health" cards were the main source of information on the intervention, rather than the specially designed posters. Women did not generally discuss child health matters outside the clinic, and information about the intervention percolated slowly through the community. Although there were some rumours about sulphadoxine pyrimethamine (SP), it was generally acceptable as a drug for IPTi, although mothers did not like the way tablets were administered. There is no evidence that IPTi had a negative effect on attitudes or adherence to the expanded programme on immunisation (EPI) or treatment seeking or existing malaria prevention. CONCLUSION: In order to improve adherence to both EPI and IPTi local priorities should be taken into account. For example, local women are often more interested in weighing than in immunization, and they view vaccination and IPTi as vaguely "healthy" rather preventing specific diseases. There should be more emphasis on these factors and more critical consideration by policy makers of how much local knowledge and understanding is minimally necessary in order to make interventions successful.