The presumed advantages of day-case surgery are often based on the argument that this kind of surgery induces less psychic harm in children than inpatient care. However, medical psychologists in particular increasingly prefer short-term hospitalization with rooming-in or daily visits by the mother. Neither opponents nor supporters of day-case surgery could produce valid findings from controlled and methodically valid studies of this subject. MATERIAL AND METHODS. A controlled, prospective study of the psychogenic effects of non-acute surgery under general anesthesia in children between 2 and 6 years of age was performed. The childrens' psychologic alterations were measured 6 and 12 weeks after the operation using a structured interview of the mother. Twenty-four children were treated by day-case surgery, 28 as inpatients. All children belonged to ASA groups I and II. The interviewer was "blind" to the indication, kind of surgery and duration of hospitalization. The mothers' answers concerning the postoperative behavior of their children were coded in terms of frequency of changes (seldom, unchanged, more frequent) or intensity (vigorous, unchanged, slight) in comparison to the time before operation. The data were compared to the anxiety of the children and mothers before premedication. The childrens' anxiety was measured using the scoring system of Büttner and Breitkopf; the mothers' anxiety was measured using a modified scoring system according to Groeger and Grosse-Aldenhövel. RESULTS. 1. There were no significant differences between the day-case and the stationary groups, in either preoperative anxiety assessments or postoperative psychological findings. 2. In comparison with the total number of possible psychologic effects, the number that really occurred was very small; only in 6 of 81 items did more than one-third of the mothers report any changes. 3. Most items were reported as minimal changes. Therefore, all items had to be analyzed using the method of analysis of factors (mean components, varimax rotation, Scree-test). Within 44.7% of extracted variance there were 2 factors involving behavior. Items applying to factor 1 included disturbed sleep and increased attachment of the child to the parents, indicating "emotional confusion" or "troublesome behavior." Factor 2 indicated a more flexible manner of playing and increased ability to concentrate.4+