Data obtained from a motivational assisted spirometry system (MASS) and a regular spirometry system was compared. Paired tracings of forced expiratory volume (FEV), forced vital capacity (FVC), expiratory flow rate of 25 to 75 percent FEV (MMEF) flow rate at 50 percent FEV (FEF50), and time of FVC (EOT) for 600 subjects, and of peak flow (Pk) for 571 subjects, were coded on data cards and entered into a computer for analysis. FVC and FEV values were lower on the MASS system while PK and FEF50 values were increased. No differences were seen in MMEF and EOT. The authors recommend several considerations for future evaluations of the MASS, including system operation time, data pool size, and the influence of testing conditions. Also recommended is the conversion of MASS test results to more conventional measurement units.