The General Framework requires case studies to progress its development. Case studies of HCI design knowledge can be successful or unsuccessful. Successful case-studies are considered to fall within the scope of the design knowledge being applied. Unsuccessful case studies are considered not to fall within its scope. Thus, successful and unsuccessful case studies together define the scope of the application of HCI design knowledge.Case studies are of two types: of the framework itself and of the HCI knowledge, acquired with its support by means of HCI research. In turn, these two types of case study can be divided into acquisition and validation case studies. The latter types of case study have yet to be carried out for the General Framework, comprising concepts of discipline, general as common, general problem, particular scope, general research, general knowledge and general practices. However, on the basis of case studies reported in the literature, and the validation proposal made here, suggestions are made as to the research needed to conduct such case studies.