Introduction: The United States spends a higher percentage of its gross domestic product on health care than any other country. Previous efforts to curtail health care spending have had minimal impact. We hypothesized that informing physicians of the cost of expensive cardiovascular diagnostic tests would change their ordering behavior. Materials and Methods: Hospitalist physicians (n = 38) were randomly assigned to either seeing or not seeing the cost of diagnostic tests, via a computer pop-up screen, at the time of order entry. Patients were inpatients on a general medical service. Cost-aware physicians were shown the cost of the test they ordered as well as the cost of similar tests with different costs. There was a 4-month baseline period prior to randomization followed by a 4-month intervention period. The primary outcome measure was a change in the proportion of imaging stress tests in the study period. Results: Of the total number of stress tests ordered (imaging and nonimaging), cost-aware physicians ordered 89% of their tests with imaging during both the baseline and study periods. Cost-unaware physicians ordered 91% imaging tests during the baseline period and 87% during the study period. There were no significant differences between the groups regarding change in ordering from baseline to study period. Both groups showed a slight increase (P < 0.03) in ordering the more expensive regadenoson nuclear stress tests (cost-aware: 30% baseline, 44% study period; cost-unaware: 36% baseline, 41% study period). Discussion: Informing physicians of the cost of certain diagnostic tests is not a sufficient intervention to influence their ordering behavior.