Background: In most Western countries the growing gap between available resources and greater potential for medical treatment has brought evidence-based guidelines into focus. However, problems exist in areas where the evidence base is weak, e.g. elderly patients with heart disease and multiple co-morbidities. Objective: Our aim is to evaluate the views of Swedish cardiologists on decision-making for elderly people with multiple co-morbidities and acute coronary syndrome without ST-elevation (NSTE ACS), and to generate some hypotheses for testing. Methods: A confidential questionnaire study was conducted to assess the views of cardiologists/internists (n = 370). The response rate was 69%. Responses were analyzed with frequencies and descriptive statistics. When appropriate, differences in proportions were assessed by a chi-square test. A content analysis was used to process the answers to the open-ended questions. Results: 81% of the respondents reported extensive use of national quidelines for care of heart disease in their clinical decision-making. However, when making decisions for multiple-diseased elderly patients, the individual physician's own clinical experience and the patient's views of treatment choice were used to an evidently greater extent than national guidelines. Approximately 50% estimated that they treated multiple-diseased elderly patients with NSTE ACS every day. Preferred measures for improving decision-making were: (a) carrying out treatment studies including elderly patients with multiple co-morbidities, and (b) preparing specific national guidelines for multiple-diseased elderly patients. Conclusions: In the future, national guidelines for heart disease should be adapted in order to be applicable for elderly patients with multiple co-morbidities.