This study develops a model for determining the standard cost of a day's admission to a Day Hospital in a rehabilitation unit. The task is carried out by analysing the costs in a single hospital. The method chosen to determine the standard cost of a day's admission to the Day Hospital was to evaluate the patient's management course. The analysis was limited to the period between the moment the patient is contacted for Day Hospital treatment up to end of the day spent in the Day Hospital. The work has four stages: 1. definition of the patient's management course; 2. identification of all the activities carried out and all the resources involved in the different stages of the management course; 3. evaluation of the resources used by the activities identified, 4. analysis of the clinical records to verify that the management actually provided did not differ from the defined one in order to determine the standard cost.