Functional residual capacity (FRC), vital capacity (VC), and its subdivisions, inspiratory capacity (IC) and expiratory reserve volume (ERV) were measured by spirometry in 140 healthy children (74 boys and 66 girls), aged 6–15 years. Total lung capacity (TLC) and residual volume (RV) were calculated on the measured lung volumes. The coefficient of variation was calculated on three successive determinations of IC, ERV and VC and on the calculated values of TLC and RV. The coefficient of variation is considerably large in the RV determination (up to 8,5%) (reflecting the influence of the individual’s cooperation during the measurement of ERV) but it is small in the TCL determination (up to 1,9%) (reflecting the reproducibility of successive measurements of IC and FRC, which is satisfactorily small). A certain training effect could be observed on the final value of successive measurements of some lung volumes, but nevertheless, this individual adaption is slight (expressed in ml) and without practical clinical importance. The relationship between lung volumes (FRC, VC, TLC, RV) and height, weight, age, and surface area, respectively, have been calculated by regression calculations. Standing height is the best independent variable for predicting lung volume except in the determination of VC in girls. However, this discrepancy between the predictive equations of VC versus standing height in girls and the other equations, published in this study, is so slight, that it is of no practical importance. The calculated residual standard deviations of all lung volumes correspond to the values, published by Engstrom et al. (1956) but are quite different from the results of Geubelle and Breny (1969), whose results are much higher. This discrepancy has been discussed as being caused by the different populations, examined in these studies. FRC, VC, TLC, and RV are larger in boys than in girls, and these differences are significant. In absolute values (i. e., expressed in ml) these differences are small compared to the corresponding actual values of lung volumes. The growing rate of the lung volumes according to the standing height is similar in boys and girls. The mean values (and 2 SD) of the FRC/TLC as well as the RV/TLC ratios were calculated for both boys and girls, being almost identical to those, published in literature. There is a slight but significant change of these ratios in relation to age in boys but not in girls. This significant correlation to age in boys is so small, that it is negligible from the practical point of view.