Objectives -to determine the normative data of sentence speech intelligibility in a free sound field and to estimate the applicability of the Russian Matrix Sentence test (RuMatrix) for assessment of the hearing aid fitting benefit. Material and methods. 10 people with normal hearing and 28 users of hearing aids with moderate to severe sensorineural hearing loss were involved in the study. RuMatrix test both in quiet and in noise was performed in a free sound field. All patients filled in the COSI questionnaire. Results. The hearing impaired patients were divided into two subgroups: the 1st with high and the 2nd with low hearing aid benefit, according to the COSI questionnaire. In the 1st subgroup, the threshold for the sentence intelligibility in quiet was 34.9 ± 6.4 dB SPL, and in noise -3.3 ± 1.4 dB SNR, in the 2nd subgroup 41.7 ± 11.5 dB SPL and 0.15 ± 3.45 dB SNR, respectively. The significant difference between the data of both subgroups and the norm was registered (p