Geographical differences in the frequencies of eight common surnames in Jutland (Denmark) are analysed using data from telephone directories of 121 exchanges. All the names showed a significant geographical surplus variance, which was divided into trend and patchiness components reflecting the history of the names. The surplus variance of surnames with restricted areas of origin was dominated by a large trend component; for surnames with an originally more even distribution, the patchiness component was dominant. The patterns of distribution were affected by processes which modelled natural selection with linkage disequilibrium. The combined patchiness within the clusters of exchanges gave information about patterns of local migration and level of social integration in the communities. Areas situated in boundary regions show high levels of patchiness.