OBJECTIVES: To develop and validate a disease-specific health status measure for individuals with myocardial infarction (MI). METHODS: The development of the Myocardial Infarction Dimensional Assessment Scale (MIDAS) followed three main stages.  Stage 1 consisted of in-depth, semi-structured, exploratory interviews conducted on a sample of 31 patients to identify areas of salience and concern to patients with MI.  These interviews generated 48 candidate questions.  In stage 2 the 48-item questionnaire was used in a postal survey to identify appropriate rephrasing/shortening, to determine acceptability and to help identify sub-scales of the instrument addressing different dimensions of MI.  Finally, in stage 3 the construct validity of MIDAS subscales was examined in relation to clinical and other health outcomes. Setting - A single centre (district general hospital) in England was used for stages 1 and 3 and a national postal survey was conducted for stage 2. Patients - A total of  410 patients were recruited for the national survey (stage 2).  Full data was available on 348 (85%) patients.  155 patients were recruited to test construct validity (stage 3). RESULTS: The MIDAS contains 35 questions measuring seven areas of health status: physical activity, insecurity, emotional reaction, dependency, diet, concerns over medication and side effects.  The measure has high face, internal and construct validity and is likely to prove useful in the evaluation of treatment regimes for MI. CONCLUSIONS: The MIDAS has acceptable validity and reliability.  It is suitable for use in a variety of settings for patients with myocardial infarction.