The assessment of respiratory system performance may involve issues such as pulmonary gas exchange, respiratory mechanics, oxygen transport and other factors. This paper describes an MS-DOS program called Respiratory Consultant that was designed for use with a hand-held MS-DOS computer, but can also run under Windows 3.1 and Windows 95 if desired. Respiratory Consultant performs a number of computational tasks potentially appropriate to respiratory care in the ICU and elsewhere. These include: predicted arterial oxygen tension from age, interconversion of oxygen tension and saturation, calculation of gas exchange indices and oxygen transport parameters, dead-space estimation, and pulmonary function test interpretation. Respiratory Consultant is freeware that will run easily on most IBM-compatible PCs and may be downloaded from the Internet.