This is a study of the ventilatory functions of 1,805 normal Mexican-American, white, and black students of six public schools in Houston, Texas, with ages ranging from 7 to 20. A roll-seal piston type spirometer was used. The best performed forced vital capacity curve of each student was selected by the computer program from which the following measurements were extracted: FVC, FEV1, FEV1/FVC ratio, PEFR, and MMEF. Each student also had the peak expiratory flow rate measured by the Wright peak flowmeter to establish normal values with this instrument. Significant differences of lung volume and flow rate exist among the three races, and between male and female subjects. Prediction equations and prediction curves for each race and sex are presented. The results of the present study are compared with those of previously published works.