BACKGROUND: Secondary prevention is important in preventing new cardiovascular events after acute myocardial infarction (AMI). AIM: To explore patients' experiences of secondary prevention after a first AMI. METHODS: A qualitative approach with hermeneutical analysis of in depth interviews was used. RESULTS: Twenty patients (12 men and 8 women, aged 34-79 years) were interviewed. None of the patients was previously treated for cardiovascular disease except one that had a history of angina pectoris. Two main themes emerged from the analysis. 1) Impact of medication: patients interpreted bodily sensations as a consequence of being medicated rather than as a result of their heart attack. The medication led to feelings of being intruded upon but also to positive feelings of security. 2) Impact of health professionals: communication with health professionals resulted in confusion about both treatment and the severity of the coronary disease. Patients expressed a need of being reassured by their physician regarding their physical status. CONCLUSIONS: Health professionals need to consider the impact of pharmacological treatment on patients' life, at least in patients who suffer from a first AMI. The point of departure in secondary preventive work must be patients' beliefs about their condition and the treatment they receive. Nurses and physicians must be aware of the information each patient has been given, and from this starting point, they have to be in concordance with one another. From the patients' perspective it is deemed necessary for the physicians to discuss the disease and the consequences it may have, both in the near future and in the long run, as soon as possible.