A study has been made of the demographic and genetic structure of the Moray Firth fishing communities of Gardenstown and Whitehills. It was intended to investigate population composition, genetic structure and microevolutionary processes in a mainland community where occupation has played an important social role in the population. In this study, those who depended upon the fishing industry for a livelihood have been compared and contrasted with nonfishers. Chapter One consists of a description of the geographic and social setting and a discussion of the historical and economic background of each community. The next chapter, a literature review, details the scope of published literature on different aspect of population structure. Chapter Three describes the techniques and methods applied in this study. This chapter also describes the sources, and discusses the quality, of the raw data. Chapter Four, the first chapter containing results, concentrates on the demographic structure of the population. The theme of Chapter Five is devoted to surname analysis. The frequency and distribution of surnames through time and by occupation has been described and discussed. Very distinct occupational differences arose here, strongly suggesting, on the basis of comparative findings, that the fishers formed a partially isolated, closely related subdivision of the population. A detailed analysis of marital isonymy has been made and secular and occupational trends in the coefficient of inbreeding, as estimated by the method of Crow and Mange have been obtained. In an occupational comparison, it is clearly seen that inbreeding coefficients for the fisher population of each communities were significantly higher than values obtained for the non-fisher group. These differences, which would have produced differences in genotype distribution have been interpreted on the basis of differences in economic demands of the two sub-populations. Characteristics of marriage and marital movements have been considered in Chapter Six. The frequency of marriage, distribution of age at marriage and seasonality of marriage have been described. In this latter, fishers and non-fishers show clear differences, fisher marriages displaying a sustained tendency towards winter occurence. Endogamy rates have been examined through time and by occupation. There has been a clear secular decline in this trait, indicating that the population has become less localised. For exogamous marriages, the magnitude and direction of marriage distance has been investigated. A, consequence of marriage, fertility, was examined in the next chapter. Female fertility has been determined as have birth intervals and occupational differences in family sizes. It has been found that family size amongst fisherfolk was larger, and also that there were differences in fertility history between migrant and sedentary couples. The potential impact of differences in fertility and mortality patterns for the action of Natural Selection in these populations has also been considered in this chapter. Despite some criticisms of the method, the potential for natural selection to operate in these populations has been estimated to be high. Chapter Eight, the last chapter of results, describes the initiation and application of a computer technique for the reconstruction of individual life histories, and the establishment of family groups. The amount of in-migration to and out-migration from different sections of these communities has also been quantified. The last chapter provides an integrated discussion on the basis of overall occupational, secular, and village patterns for the two communities.