This paper presents a case study of a discrete event simulation model of an Accident and Emergency Unit in a hospital in the UK. The objective of the study is to create a simulation study of the A&E Unit, to evaluate alternative scenarios and hence reducing patient waiting time. The case study uses a novel approach to predict the arrival time of patients and hence results in a more realistic platform on which to base the subsequent scenario analysis. The scenario analysis illustrates that significant reductions in the waiting time of patients can be obtained by relatively minor changes in operations.