OBJECTIVE: To illustrate the use of decision trees with a utility index in clinical decision making. METHODS: A decision tree was created related to whether or not to perform a tonsillectomy. Data from the literature were applied to a common hypothetical clinical scenario. RESULTS: A decision tree graphically represents the typical decision-making process that many clinicians use. The addition of utility functions permitted consideration of the adverse or beneficial effects of outcomes, altering the treatment decision. CONCLUSION: Quantitative tools such as decision trees may quantify outcome preferences and aid in clinical decision making, but the proper tool and background data are essential.