This study has been performed in order to evaluate a prototype for the human - computer interface of a computer-based speech training aid named ARTUR. The main feature of the aid is that it can give suggestions on how to improve articulations. Two user groups were involved: three children aged 9 - 14 with extensive experience of speech training with therapists and computers, and three children aged 6, with little or no prior experience of computer-based speech training. All children had general language disorders. The study indicates that the present interface is usable without prior training or instructions, even for the younger children, but that more motivational factors should be introduced. The granularity of the mesh that classifies mispronunciations was satisfactory, but the flexibility and level of detail of the feedback should be developed further.