Observations based on a high yield indication list (HYL) revealed that 80% of posttraumatic skull radiographs requested by physicians were not indicated. To investigate this possible overuse of radiography, 15 resident physicians who had used the HYL in a university emergency room were interviewed. The interviews included a questionnaire, case simulations, and discussion of actual head trauma patients. Several general reasons for the overuse were detected: (1) overriding indications to the HYL; (2) basic problem-solving strategies of the physicians (pattern recognition, method of exhaustion, and hyopthesis generation and evaluation); (3) the context of the decision-making (patient and family expectations, mentor and peer pressure, malpractice threat, time management concerns); (4) fear of uncertainty; and (5) routines. It was found that overuse of diagnostic radiography was not perverse or irrational, but was produced by a complex mixture of actual expectation of yield from the procedure, personal approaches of the individual physicians, and pressures in the decision-making environment.