Objective – To verify if the foreign population resident in the Canton Ticino, differs in the use of public psychiatric services and in the type of mental disorder presented, with respect to the Swiss population. Design – Research completed on subjects Swiss and foreign, over 19 years old, and resident in the Canton Ticino, who during 1995 spent at least one day admitted at the psychiatric hospital or had at least one contact with the out—patient services. Setting – Public psychiatric services of the Canton's sociopsychiatric organisation. Main outcome measures – For the Swiss, Italian and other non-Italian foreigners, the standardised annual rates of in- and outpatient prevalence and first admission and first outpatient contact were calculated, both totals and per diagnostic categories (ICD-10). Results – The group of non-Italian foreigners presents higher total standardised annual rates of in-patient prevalence and first admission and above all, of first admission, with respect to the Swiss and Italian groups; furthermore, with respect to the other two groups it presents higher first admission rates for the schizophrenic syndromes (F2) in men and for mental disorders due to psychoactive substances (Fl) in women. Whereas for first outpatient contacts the other foreigners present higher rates in neurotic syndromes (F4) in men, and affective syndromes (F3) in women. Conclusions – The results seem to confirm the presence of higher levels of mental disorder in non—Italian foreigners, above all for certain nationalities, with respect to Swiss and Italians. It is possible that the presence of a substantial offer of psychiatric services from the private sector may have caused an underestimation of the actual rate of mental disorder above all in the Swiss group and to a minor extent in that of the Italians.