Eighty-five Italian and forty-nine Swedish patients consecutively admitted for compulsory treatment to either an Italian or a Swedish psychiatric unit in selected areas of the two countries have participated in an exploratory study aimed at assessing the main characteristics of compulsory admitted patients, and in particular, the immediate reason for admission. The two series proved to be quite similar as concerns most sociodemographic variables, and as concerns clinical diagnosis and severity of the morbid condition at admission as measured by means of a rating scale. More Swedish than Italian patients lived alone when admitted to hospital, and for more of them the request for admission was made by other people than relatives, and a larger proportion of them was accompanied to the hospital by medical or social welfare personnel. In both series the largest proportion had a low educational level and belonged to the lower social groups. The same proportion in the two series had previous admissions. The most common reason for admission was "odd or improper behaviour" for the Swedish patients, and "feared or manifest dangerousness" for the Italian patients. The Italian patients remained at hospital on average half the time than the Swedish patients.