The paper focuses on the visual-auditory method of analysis for utterances of stuttering people. The method can be classified as an intermediate solution which is in between a traditional auditory and automatic methods. The author prepared a special computer program DiagLog, with the aim of carrying out the visual-auditory analysis, which can be used by logopaedists to make a diagnosis. The speech disfluencies are assessed by means of the observation of the spectrum and the envelope of fragments of recordings with simultaneous listening to them. A collection of 120 a few-minute recordings of 15 stuttering people was used to verify the correctness of the method and to compare it with the traditional auditory technique. All the samples were analysed by means of the auditory and the visual-auditory method by two independent experts. Consequently, the diagnosis using an additional visual aspect proved itself to be more effective in detecting speech non-fluencies, in classifying and measuring them.