In an attempt to examine the possibility of selection on domestic cats populations in the urban environment, a number of surveys were conducted in four contrasting areas of Glasgow--two near either extreme of Western, industrial socioeconomic status. The first survey was in the form of a questionnaire to inhabitants enquiring of preference for a particular phenotype. This survey revealed a consistent preference for lighter phenotypes in all areas. The incidence of cat ownership was greatest in the two affluent areas where there was also a high risk of the cat being sterilised. Independent of the questionnaire survey was a study of cat coat colour gene frequencies in each of the four districts. This study revealed that darker phenotypes predominate in the two areas of lower socioeconomic status, Maryhill and Govan. To date, the cat populations in these two areas are the darkest to have been described in the world. In contrast, a lighter phenotype was found in cats inhabiting the two districts of higher socioeconomic status, Kelvinside and Bellahouston. This difference in phenotypic darkness was also paralleled by appropriate clines in coat colour gene frequencies. The results demonstrate that human preference is not effectively translated into selection at any of the loci considered. In situations where human preference is most likely to occur, neutering risk is also high. Although the force responsible for the darkening of phenotype has yet to be identified, the fact that the darker alternative allele at each of the O, a, t, d, S and W loci is favoured suggests that selection is operating on these polymorphic coat colour loci.