This exploratory study is designed to answer “what happens when the clients complain that the delivered Information Systems (IS) don’t match their expectations?” This discrepancy between client expectations and the client perceived system performance at the time of system delivery can be described as a “gap”. The “gap” phenomenon, the failing to match client expectations with the delivered system, will lead to client dissatisfaction, system rejection, and project failure. Since we know little about the “gap” phenomenon, and no literature has directly and systematically investigated this phenomenon before, an exploratory qualitative study was conducted to answer (1) what the gap is; and (2) how and why the gap is generated in the IS development process. Focus group interviews were conducted with project managers, developers and consultants from four leading IS developing organizations. This paper reports the findings of the first part of the exploratory study. In this study, two dimensions of the gap – the possible areas of the gap and the forms of the gap are identified and four types of the gaps are classified based on the two dimensions. We then adopt a process view to investigate how the gap is generated in the IS development process. To assist the discussion and investigation, we defined four sub-gaps – requirements definition gap, system design gap, construction gap, and system delivery gap. Propositions are proposed and a gap model is developed to explain the relationship between the four sub-gaps and the final gap.