Mainstream sociological studies of intergenerational social mobility have emphasised social factors such as education and the material and cultural resources of the family of origin as the main influences on the chances and direction of social mobility. Medical sociology in contrast has been more interested in its physical correlates such as height and health status. Data from the West of Scotland Collaborative study allow an examination of the relationship between social mobility and both social and physical factors. Height, education and material circumstances in the family of origin, indexed as the number of siblings, were each independently associated with the chances of both upward and downward social mobility in this dataset. In each case the net effect of this social mobility was to constrain the social distribution of these variables. Any role which these factors may play in indirect health selection, it is argued, cannot account for social class differences in adult health.