The efficacy of sound reinforcement at two bandwidths (high frequency at 250-5000 Hz and low frequency at higher than 1000 Hz frequencies with a steepness of 14 dB in the octave) in the hearing aids of children with hypoacusis was investigated. Altogether 67 children at the age of 11 to 14 years with an average hearing impairment of 35 to 97 dB were examined. In the low frequency range, 3% of the children showed a better, 33% a lower and 64% an unchanged discriminatory capacity of speech when compared to the high frequency range. The lack of the filtration effect on the discriminatory capacity was seen in children with a moderate hearing loss at high frequencies (in 50% children) due to adequate hearing perception at the above bandwidths or in children in whom hearing thresholds at 2000 and 4000 Hz were so high that failed to provide proper speech perception at both bandwidths. Therefore when hearing aids are regularly used, the high frequency range of the spectrum is sufficiently informative for the overwhelming majority of children with hearing loss, i. e. for 83%. These results give evidence that a high frequency range is adequate for children with hearing loss if they begin to use hearing aids from an early stage.