The ratio of the vital capacity to the maximum phonation time (Phonation Quotient; P. Q.) and the ratio of the maximum expiration time to the maximum phonation time (Expiratory Expenditure Index; E. E. I.) have often been used for clinical evaluation of vocal function or the efficiency of the larynx on phonation. Although the ranges of P. Q. and E. E. I. in normal adults have already been reported by previous investigators, those values in normal children are hardly available in the literatures. The present authors attempted to measure the vital capacity, the maximum pho-nation time and the maximum expiration time in 1075 normal children in primary and junior high schools in Osaka city, from which P.Q. and E.E.I. were obtained. For each age group, the standard values of P. Q. and E. E. I. were calculated by the regression analysis, while the upper limits were given by antilogarithmic transformation (90% quantile) . The results were summarized as follows;
1) In general, P. Q. and E.E.I. in children are markedly lower than those in adults, though the differences become lesser when the age of children increases.
2) The standard value of P. Q. appears roughly comparative to the height (cm) of children in respective age range, while that of E. E. I. to 1/20 of the body weight (Kg.) .
