Coronary heart disease (CHD) is the most important cause of death in the UK. Evidence suggests that between 5,000 and 10,000 deaths per year could be prevented if thrombolytic therapy were to be administered within 12 hours of the onset of symptoms of a heart attack. As part of the requirements of the National Service Framework for CHD, health authorities will be expected to produce detailed plans and protocols which describe pre-hospital service care models. Included in these will be public education campaigns aimed at encouraging people to call 999 for an ambulance in the event of symptoms suggestive of a heart attack. The aim of this study was to explore lay decision-making at the time of a cardiac event and address the question of why people do not call 999 for an ambulance. A sample of 43 patients, admitted to two district general hospitals who had survived a cardiac event, and 21 relatives or bystanders who were present at the time of the event, were interviewed. The interviews were tape-recorded, transcribed verbatim and analysed using the constant comparative method. There was variation in who made the decision to call for medical help and even after the decision was made, delays occurred due to interaction between patients and relatives or bystanders. An ambulance was called by informants in only two cases, two drove or were driven to hospital, 34 asked the general practitioner (GP) to call and five visited the GP at the surgery. Factors influencing these actions included a perception that GP services were faster and more accessible than ambulance services, misconceptions about the seriousness of the situation, misconceptions about the correct 'procedure' or way to access emergency services and a range of personal and contextual factors. The data suggest that public campaigns to encourage people to call 999 for an ambulance in the event of symptoms of a heart attack may be ineffective unless they address lay understandings and concerns about accessing emergency services.