Office spirometry is an integral part of the evaluation of any patient with known or suspected lung disease. Though accurate and affordable bellows-type spirometers are available to clinicians, the available microprocessors that calculate test results markedly increase the cost of the equipment. I have successfully used an inexpensive pocket computer programmed to provide predicted values and interpretation of test results, printing this information in a format suitable for mounting in the office chart. The reliability of the results and interpretations permits convenient and low-cost pulmonary function testing in office patients when clinically warranted.