Investment appraisal techniques (TAT) range from quantitative (financially based) techniques to qualitative (non-financially based) techniques, and represent tools that may be applied during IT/IS evaluation to assess the impact (value, worth or usefulness) of information systems on the organisation. The normative literature review demonstrates that decision makers need to better evaluate their systems as the role of IT/IS systems in organisations and global expenditure on IT/IS continue to rise. In the service oriented public sector, the normative literature indicates that whilst decision makers may continue to depend on financially based TAT to evaluate IT/IS project that cut cost, they may be doing the populace a disservice by not focussing on non-financial benefits of IT/IS (such as improved customer service). This dissertation investigates the application of TAT in the public sector. To do so, a conceptual model is developed to represent the effect of barriers to the application of IAT. The conceptual model is underpinned by three proposition, which indicate that the organisational investment process, time available for evaluation, and fund accessibility can impede the application of TAT. To test the propositions, a suitable research strategy is selected and developed that essentially adopts a multi-case study for the purpose of testing the proposition, and trialling the applicability of the conceptual model in the public sector. In doing so, the multi-case study investigation is used to produce a frame of references that may be employed by decision makers to recognise barriers to the application of TAT. The frame of reference represents the dissertation's contribution to the body of knowledge. The empirical evidence demonstrated that barriers, as suggested by the propositions, do surface in all case studies, thus confirming them as permanent elements in the frame of reference. The empirical evidence also demonstrated that the application of traditional IT/IS life-cycle models was not possible where inherited IT/IS systems were considered, as inherited systems did not have a definitive start/stop point.