The North-Swedish population is a mixture of Finnish, Saamish and Central-Swedish ethnic groups. We have studied the Finnish and Saamish admixture by means of genetic markers in 23 North-Swedish subpopulations. The Finnish influence was estimated using the transferrin genes B0-1, DCHI and C3 and the enzyme gene SOD1*2, and markers for Saamish influence were the blood group gene ABO*A2, the serum group gene GC*1F and the enzyme gene 6PGD*C. In the subpopulations the Finnish influence (admixture) varied between 0 and 84% and the Saamish influence between 0 and 34%. The Saamish influence was strongest in the western and northern parts of the area. In the northern part of the area, between 1/4 and 1/3 of the gene pool of the present-day population may be Saamish in origin. The Finnish influence was strongest in the northern and northeastern parts of the area. In the subpopulations along the Finnish border, between 60 and 80% of the gene pool may be Finnish in origin. Significant correlations were found between the Saamish marker genes and between the Finnish marker genes. Due to geographical overlapping of Finnish and Saamish influence, significant correlations were also found between Finnish and Saamish marker genes. The geographical pictures of Saamish and Finnish influence in northern Sweden showed a fair agreement with the expectations derived from historical knowledge. Although a substantial part of the genetic heterogeneity of the North-Swedish population is ethnic in origin, it is obvious that founder effect and genetic drift also have played an important role.