Guidelines for ordering preoperative spirometry have been proposed by GM Tisi (1979) and more recently by the American College of Physicians (ACP). Requests for preoperative spirometries represent a significant portion of all requests for screening spirometry at our institution and utilize significant man-hours of technician time. We determined the percentage of these requests that did not meet the ACP guidelines and characterized why these requests were being generated. We sampled 441 screening spirometries performed by the Walter Reed Pulmonary Function Laboratory over a 4-week period. One hundred thirty-eight (31%) of these were done preoperatively and complete data were available in 135 cases. Patients in the analyzed group had a mean age of 59 years (±14 years), ranging from 20 to 84 years of age. Fifty-two (39%) requests did not meet ACP guidelines. Most of these requests were associated with either normal spirometry (n=34) or only mild spirometric abnormalities (n=14). Spirometry revealed severe obstruction in only one case when the request was not indicated. No cases of moderate obstruction, severe restrictive pattern, or possible upper airway obstruction were found in the group of requests in which spirometry was not indicated. Of the requests that did not meet ACP guidelines, 21 met Tisi's broader guidelines. Most of these requests were found exclusively in patients older than 70 years of age (n=13) and the morbidly obese (n=4). Of the 31 studies that did not meet either set of guidelines, 25 occurred in asymptomatic, current, or prior smokers. In conclusion, during a 4-week study period at our institution, 39% of preoperative spirometry requests did not meet ACP guidelines. Most of the patients had been referred because of age greater than 70 years, morbid obesity, and a current/prior history of smoking. However, the literature does not support obtaining preoperative spirometry in such patients except for those undergoing only lung resection. We recommend stricter adherence to the ACP guidelines as a means of decreasing the number and cost of unnecessary spirometries being performed.