Of the different psychic function disturbances which may occur during the postnarcotic phase, those showing symptom complexes with sensory, neurotic-emotional or psychotic reactions mostly diminish within some hours or a few days. On the other hand, a great many patients suffer from individual mental problems of which concentration and memory weaknesses are the main characteristics, sometimes outlasting the surgical operation by a number of weeks or even months. The results of a preliminary examination of 520 patients, recently released from surgical departments, confirmed that 30% suffered from prolonged memory disturbances. Of a control group of patients treated with local anesthesia only 6% of 69 persons questioned had been aware of such symptoms. In the consecutive analysis of 90 surgical patients, making use of psychometric test methods such as digit span, learn- and memory test (German abbreviation LGT1) and concentration test d2, no reduction of memory capacity could be ascertained. An additional questioning of these patients about subjectively experienced disturbances, in comparison with the preliminary examination, resulted in approximately identical statements. The aetiology of subjectively experienced impairment of memory and concentration during the later postoperative phase appears to be still insufficiently clarified, for which psychogenic factors must be taken in consideration.