This article presents some preliminary results from a historical study of social mobility in Britain and Ireland, from the late eighteenth to the early twentieth century. The study is marked by a unique combination of features: (1) it follows families for up to Þve generations, through both maternal and paternal lines; (2) it uses a continuous measure of social position, rather than class categories; (3) this measure is derived from data on social interaction – correspondence analyses of cross-tabulations of the occupations for marriages taking place in the periods 1777–1866 and 1867–1913; (4) each individual's social position is summarised by a work-life trajectory, represented by his social location at ages 20 and 50. The analyses are based on twelve ten-year birth cohorts from 1790–99 to 1900–09. The results indicate a remarkable degree of stability of social processes of reproduction throughout this period, although there is an extremely slow shift towards a weakening of family influence. This process appears to have accelerated for those born in the last quarter of the nineteenth century, a period of both educational reform and major change in Britain's industrial organisation.