Usability evaluation results in several usability problems and the non-UE developer is often not a part of the evaluation as it might deter the participant from reporting all the errors and also, conducting usability evaluation is a usability engineer's responsibility. Thus the evaluator needs to create unambiguous usability problem reports, which will help the developer fix the usability problems. This research involves the development and evaluation of the Usability Problem Diagnosis tool, which supports problem diagnosis through analysis and storage in a common database shared between the evaluation and the development team. This tool uses the User Action Framework as an underlying knowledge base to support problem diagnosis. / Master of Science