Many criticisms can be made of the practice of dividing the population into social classes solely on the basis of occupation. This paper reports the results of an attempt to improve one aspect of such classifications (The Registrar General's Classification). The lowest social class (social class V) is the most heterogeneous of all the classes; it is suggested that it can usefully be subdivided into a ‘stable’ and an ‘unstable’ social class. Into the stable class (V) go the steadily employed, though unskilled, men and their families. Into the unstable class (V) would go those families most lacking in skill and property, signified by long-term or frequent unemployment, or the complete absence of a male head of the household. An attempt is made to justify this subdivision both theoretically and empirically by the demonstration that there are significant differences between social classes V stable and V unstable with regard to selected social class attributes.