In this cross-cultural, nation-wide study including all immigrant groups in Sweden, over 10,000 suicides and undetermined cases occurring during the period 1987-1991 were analysed. Diagnoses of the underlying causes of death were classified according to ICD-9, all of the alternatives E950-E959 and E980-E989 being selected. Definite and overall suicide rates were estimated for each immigrant group represented. We found an overrepresentation of immigrants in the Swedish suicide statistics nation-wide. A total of 15 countries (60% of the immigrant population) manifested more observed than expected suicides and undetermined cases. This overrepresentation was statistically significant among immigrants from Russia, Finland, Germany, Denmark and Norway (the immigrant population of these countries represents nearly 50% of the total population of immigrants in Sweden). Other nationalities with an increased suicide incidence were from Poland, Hungary, Czechoslovakia, Austria, Korea, The Netherlands, France, Spain and Uruguay. The risk of an immigrant dying of a cause related to suicide was found to be 1.5 times higher than that for a native Swede. Furthermore, the increased suicide rates observed among the immigrant groups in Sweden were found to be higher than in the respective countries of origin for 90% of the nationalities investigated, including those characterized by a relatively high refugee flow to Sweden, the rank order being generally the same both in the countries of origin and in Sweden. The immigrant groups with the highest suicide rates in our study were from Russia, Finland and Hungary. Suggestions are made concerning the possible involvement of underlying cultural, anthropological and genetic factors in this phenomenon.