In November 1980 the United Kingdom government introduced new regulations concerning the amount of supplementary benefit that lone parents could keep after taking account of their earnings. The purpose of the present study was to assess the effect of this measure upon the labour market participation rates of lone mothers and to evaluate its significance in relation to other factors affecting such participation. Variables Personal characteristics of lone mothers, including: marital status; tenure; number and ages of children; selected items of paid work history; economic circumstances; attitudes to labour market participation; knowledge of social security systems; and access to child care. Preferences over paid work/domestic activity combinations; take-up of means-tested benefits.