Spirometry was performed longitudinally over a period of 8 yr on 72 children (29 black females, 26 black males, 9 white females, and 8 white males) starting as early as 3 yr of age. Weighted straight-line regressions of 6 maximal expiratory flow-volume parameters--forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), forced expiratory flow during the middle half of the FVC (FEF25-75), and maximal expiratory flows after 50 and 75% of the FVC had been exhaled (Vmax50 and Vmax75, respectively) - on height were computed and were found to describe adequately the data over a height range of 100 to 150 cm. Statistical comparisons of regression lines revealed significant differences for FVC and FEV1 when white females were compared with white males, white females with black females, and white males with black males, but not for black females with black males. Regressions of FEF25-75 and Vmax50 for black females were significantly lower than for white females, and those for white males were lower than those for white females, but no differences were detected when black females and white males were compared with black males. Only white females compared with black females revealed significant differences for Vmax75. There were no significant differences for any of the comparisons for PEF. The data presented expand the age range for evaluating lung function in children, indicate the feasibility of testing pre-school-age subjects, and provide new approaches to analysis of longitudinally collected information.