Hospital care has been subject to important changes during the last century. In stead of treating patients with various diseases with bed rest, medical care has shifted from in hospital to an ambulatory or outpatient setting as much as possible. Admission time after surgery shortened and day surgery became popular. The central theme of this thesis was to assess the developments of day surgery in the Netherlands in the past two centuries and to address several relevant clinical issues. Data on clinical and day care admissions were provided by Prismant, Utrecht. First, developments from 1984-1995 were assessed and a future scenario was formulated. Second, further developments from 1996-2004 were studied and the realisation of the previous future scenario was evaluated. Meanwhile, some aspects of day surgery in daily clinical practice were studied. The present quality of day surgery, expressed in safety, efficacy and patient satisfaction was assessed during one year in a general surgery department of a district training hospital. Feasibility of day surgery in morbidly obese patients who underwent laparoscopic gastric banding was studied and compared to a group who was admitted for overnight stay. The application of thrombosis prophylaxis in day surgery among Dutch surgeons and gynaecologists was assessed with an overview of current literature and guidelines on this topic. Finally, postoperative resumption of daily physical activity after laparoscopic cholecystectomy was measured in unselected patients. Day surgery showed a steady increase in the Netherlands during the past two decades until 49% of all surgical admissions in 2004. The largest growth was to be found among elderly patients. Based on data from 1995, where huge differences between hospitals existed and the fact that the current change in the financial health care system might entail a more rewarding situation for day care, a further increase in day surgery can be expected. The measurement of quality of day surgery in a Dutch training hospital showed an ...