Healthcare is a large industry faced with major challenges, such as decreasing inpatient bed numbers and increases in the share of elderly people, which require improved efficiency and effectiveness. The organisation of hospitals normally comprises highly specialised clinical departments, through which patient flows are managed. Since patient flows often involve several clinical departments, this requires much coordination both in space and time. With every individual patient having different diseases, severity levels and responses to therapy, the variability in patient flows has an impact on the inflow, internal flow and outflow at clinical departments and hospitals. Historically, healthcare resources have not been adapted to these variations. The purpose of this licentiate thesis is therefore to explore how variable patient flows are managed in hospitals. This comprises how variable patient flows affect hospitals as well as how variable patient flows are handled. It also includes the organisational configuration, and the influence it has on the actions used to handle variable patient flows in hospitals.Both the hierarchical levels, roles and teams that make decisions and manage the flow of patients as well as the actions used to handle variable patient flows at hospitals are included in the research. Hence, an approach where the hospital is regarded as a system is used, an approach often described as a system perspective. Three research methods have been used in this licentiate thesis. The first research method used was simulation modelling, to study how changes in an acute patient flow affected an emergency department and inpatient ward at a small hospital. A case study at a university hospital was performed to study both the actions used to handle variable patient flows as well as the influence of the organisational configuration. Several literature reviews, both structured and unstructured, has also been made to compare and evaluate the results from the empirical data.There are several effects of variable patient flows. The case study indicates that increased patient flow variability leads to increases in bed utilization variability and thereby problems with bed shortages. Mismatches between patient inflow and outflow, in terms of number of patients, also lead to bed shortages. Literature reviews also show that bed shortages in inpatient wards are a major cause of overcrowding in emergency departments. The results from the simulation model point toward emergency departments being more adapted to variable patient inflow than inpatient wards. To handle these issues there is a need for flexibility when providing healthcare services, something suggested in the literature.50 actions used at the university hospital to handle variable acute patient flows were identified in the research. A majority of these are used to handle the effects of the variation, not the variation itself. Nor is it effects of individual variations, such as patient inflow, that are handled but the combined effect of the variations i...