Dlagnostic strategies for coronary artery disease are diverse and include 10 exercise EKG to coronary angiography, 20 myocardial SPECT to coronary angiography, dobutamine or exercise echocardiography to coronary angiography, and direct coronary angiography. Costeffectiveness analysis can be performed considering (1) that the cost should include the costs of the diagnostic tests themselves, the cost of notdiagnosing the patients, the final test costs on false positive patients, and the cost to treat complications and 20 that the effect should include qualityadjusted life year (QAEY) with the fraction of proper diagnosis influenced by the diagnostic performance of the initial noninvasive tests. Based on the prior costeffectiveness analysis, the pretest likelihood affected most of the costeffectiveness of a diagnostic strategy. Direct angiography was most costeffective when the pretest likelihood was high (>60%), while SPECT with or without a prior exercise EKG to angiography was most costeffective when the pretest likelihood was intermediate or low. Compared to stress echocardiography, stress myocardial SPECT was more costeffective when the likelihood was moderate or high. While the prognostic significance of negative (including falsenegative) cases was important to maintain costeffectiveness of a strategy, myocardial SPECT to coronary angiography was the most costeffective method to diagnose coronary artery disease.