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Surnames can be considered as alleles of a locus which are usually transmitted patrilineally. The great abundance of surnames makes them very useful for evaluating kinship between populations, even if such kinship estimates are of limited time depth. A set of data from the island of Sardinia shows very good agreement with the Karlin-McGregor distribution of neutral alleles, and also with Fisher’s logarithmic distribution. The latter can be derived from the former; it is practically indistinguishable from it if N is large. It is easier to compute and the only parameter to estimate, v, can be obtained by a simple formula, v measures mutation plus immigration. Of the 11 dioceses, eight showed a very good fit and three showed an excess of surnames in the class of surnames represented only once. This is most probably due to the recent incorporation of the unique surnames in industrialized areas, as the correlations with statistics of development show. The logarithms of surname kinship (isonymy) show a nonlinear decrease with geographic distance between dioceses, at least in part due to heterogeneity of the slopes for surnames of different frequency. Tree analysis and principal components of isonymy are in good agreement; they show a major north-south differentiation, corresponding to the major axis of the island, and in agreement with data on genetic differentiation. East-west divergence is somewhat less important, as shown by the smaller amount of variation associated with the second principal component, and the third principal component is correlated with degree of industrial development.