A questionnaire containing 11 patient management problems was completed by 495 physicians and medical students at an American and a Canadian medical school. Respondents indicated whether they would order a particular diagnostic test in each case, given five different prices for the test. Approximately 25 per cent of attending staff and a higher proportion of residents, interns and clerks responded that they would order the test depending on its price. Approximately 50 per cent of attending staff and smaller proportions of residents, interns and clerks indicated that they would not order the test even if there were no price. Respondents in Montreal were more likely than those in Philadelphia to select a price-sensitive response, the reverse of the expected tendency. Since some tests may be ordered on the basis of price, education of physicians regarding the price of diagnostic test may alter their use of these services, but a large proportion of tests are ordered because of clinically absolute reasons, which may be insensitive to price.