In half of the patients admitted with chest pain on suspicion of an acute myocardial infarction (AMI), this diagnosis is not confirmed (non-AMI). Both AMI and non-AMI patients have a mortality which exceeds the mortality of the background population in the years following discharge based on a high incidence of cardiac death. As a pilot investigation, a comprehensive investigation programme was tested in 32 consecutive non-AMI patients. The possible organic causes of acute chest pain were thus illustrated systematically in each individual patient. In ten of the patients, a definitive diagnosis was established within the first 24 hours of admission and no further investigation was thus performed. The remaining 22 patients participated in the planned investigation programme. In 30 of the patients (94%) a probable organic cause for the chest pain was found. This investigation demonstrates that the investigation programme is employable and it suggests that the cause of chest pain in non-AMI patients usually can be placed in one of the three main groups: 1) IHS, 2) oesophageal disease and 3) physiurgic conditions.