Laboratory testing of presurgical patients has been shown to be excessive, thereby increasing costs, reducing resources for other health care uses, and increasing risks to both patients and physicians. As one step toward reducing the number of unnecessary preoperative tests ordered, we used an automated method to aid preoperative assessment of 239 patients in Chicago and in Winnipeg. The "HealthQuiz," a small hand-held device containing a computer chip and video screen, uses a decision tree to ask a minimum of 60 health-related questions (the patient's response to certain questions determines the number of questions presented). The device then generates a summary printout of patient answers, the health areas needing further attention, and the laboratory tests most likely to uncover clinically important abnormalities in that patient. HealthQuiz responses are intended to aid the physician and not to replace the personal interview. As an aid, the automated interview highlights possible problem areas for in-depth pursuit by the physician. The need for nonselective batteries of tests is eliminated because recommendations for tests are based on specific elements of a patient's history. To be effective, responses to the HealthQuiz should be the same as responses to similar questions asked by a physician. We tested that premise in this study. Patient's answers to the HealthQuiz were compared with their responses to a randomly selected set of the same questions in a personal interview. Ninety-seven percent of the response pairs were identical, and most of the 3% that differed involved changes from "not sure" replies to the HealthQuiz. Laboratory tests suggested by responses to the two methods of questioning did not differ.(ABSTRACT TRUNCATED AT 250 WORDS)