The aim of this thesis is to investigate the relationship between Finnish and non-Finnish by-names in the church registers of Nedertorneå in the nineteenth century. The investigation shows that the by-names are rather heterogeneous in character and a portion of them consists of elements from different languages. The by-names are divided into Finnish, non-Finnish and parental names, i.e. patronymics and metro-nymics. In order to study the development within the by-name stock in the rural communities of Nedertorneå and in the town of Haparanda, the numbers of Finnish and non-Finnish by-names and of parental names (including comibnations with these bynames), found within the population over the age of 20, are calculated at approximately 20-year intervals during the period 1825-1886. The investigation shows that the by-name stock in Nedertorneå is far more stable than in Haparanda. Individual changes of by-name from one selected year to the next are also taken up, together with certain causes and their possible effect on the changes in the byname stock for the population. By-name changes seem to be more common in Nedertorneå than in Haparanda. However, no real tendencies towards Swedicized forms emerge before the 1890s and the name changes tend rather to have social causes. Finally, an attempt is made to relate the number of Finnish and non-Finnish bynames (including combinations with these by-names) to certain population figures for men and women for the different selected years. The instability in Haparanda's byname stock depends on the faster population growth in the town. The value of various church registers for investigating by-names in the nineteenth century is also discussed. / digitalisering@umu