The importance of systematic usability evaluation of virtual rehabilitation systems cannot be underestimated. We have developed a virtual rehabilitation system with the functionality to guide a user through a therapeutic exercise programme. Progression is determined by users' ability to replicate movements as demonstrated by an on-screen character. Visual and auditory corrective feedback is provided during exercise in order to improve the user's postural control and biomechanical alignment. The objective of this study was to evaluate the usability of our system and subsequently implement modifications aimed at improving fidelity and ease of use. The first stage of our evaluation involved conducting an expert walkthrough with six experts currently researching in areas related to the system design. Following system refinement and modification we conducted a user evaluation study with twelve novice users using VRUSE, a computerised questionnaire-based usability evaluation tool for assessment of virtual environments. Results have provided a systematic evaluation of the system, provided information for guidance on system alterations and will allow comparison of usability levels with similar virtual rehabilitation systems tested with the same protocol. Â©2008 IEEE.