The monaural free‐field speech‐reception threshold (SRT) without and with a hearing aid was investigated for conversational sentences presented to 50 hearing‐impaired listeners. SRT without a hearing aid was measured in quiet and in noise at levels of 40, 55, 70, and 85 dBA. SRT with a hearing aid was obtained in quiet and at noise levels of 25, 40, 55, and 70 dBA. The noise had a long‐term average spectrum equal to that of the sentences. The 50 subjects were equally distributed over five degrees of pure‐tone hearing loss and five types of hearing impairment (sensorineural high‐frequency losses, with or without recruitment; flat audiogram of a sensorineural, mixed, or conductive origin). It is shown that a model of SRT as a function of noise level, developed by Plomp [J. Acoust. Soc. Am.63, 533–549 (1978)] gives a good description of the SRT values measured, both without and with a hearing aid. The data illustrate that, generally, current hearing aids do not improve speech intelligibility in noise beyond, roughly, 60 dBA.