For decades, lone mothers have been vastly overrepresented among Swedish social assistance recipients. In Sweden, social assistance is administered in the personal social services. The study aims to explore and analyse factors associated with long-term recipiency among lone mothers. The empirical material consists of micro data on 875 randomly selected lone mothers receiving social assistance in any of the three major cities of Sweden in 2007. In the analysis, a distinction is made between household demographics (e.g. ethnicity) and individual factors (subdivided into individual impairments (e.g. psychosocial conditions) and financial vulnerability (e.g. unemployment)). The main findings are: (1) even though household demographics alone show low explanatory value for long-term social assistance recipiency, analysed factors remain significant when controlling for individual factors; (2) among individual factors, only variables indicating financial vulnerability are significant. A main conclusion in the study is that social workers should be attentative that subgroups within the larger population of lone mothers have higher risk of long-term recipiency (e.g. non-native origin). Furthermore, policy revisions should be considered for this group, since personal social services extensively address individual impairments whereas long-term recipiency is strongly associated with structural factors.