Spirometric methodology for clinical and epidemiologic use in children was evaluated in 123 third and fourth grade school children 8 and 9 yr of age. They performed spirometric testing in the middle of October and again in the middle of November 1979. The results demonstrated that spirometric standards developed from adult studies can be applied to children. In addition, a minimum of 5 and a maximum of 8 maneuvers should be attempted to provide at least 3 acceptable tracings. In children, the allowable difference between the 2 best acceptable tracings of 5% or 100 ml, whichever is greater, was demonstrated to be a reasonable guideline. The results are equally reproducible when the maximal values, the mean of the 2 or 3 best values, or the values from the "best sum" tracing (the tracing with the highest value for the sum of the FVC and FEV1) are used.