The study concerns informal assistance between households as a form of social security in early 20th century Finland. Its sources consist of oral histories, tax, demographic and welfare records and household budgets. According to the study, the popular ideology related to informal assistance excluded outsiders, idealized shared poverty, relied on familiarity and reciprocity, and appealed to material imperative. It turned necessity into a virtue. In different historical situations, entitlement to assistance was attached to changing political and social circumstances, which made access uncertain, difficult, and at times, humiliating for the beneficiaries. The donors used their position to construct and reinforce their own social identities. In quantitative terms, informal assistance was relatively scarce and took various forms which followed logics that broadly resembled social security, but had significant differences. Actual gifts and assistance were more important for chronically low-income workers, whereas informal loans were related to temporary fluctuations in income, and more accessible to richer workers. Assistance in kind targeted households with many small children. In the male-dominated households of the data, informal assistance in cash was apparently controlled by men, whereas the 'informal child allowance' represented by assistance in kind was controlled by women. On the short run, recourse to informal assistance was a more significant survival strategy than adding labour to the market or taking in tenants. Statistically, the combined effect of gifts, loans and savings allowed the worker families of Helsinki participating in the cost-of-living study of 1928 to compensate approximately 36 % of intra-year income fluctuations. However, these methods offered weaker security for low-income workers than for higher-income workers. Recourse to private savings offered better protection to high-income workers than did the better chance of receiving assistance to low-income workers. The statistical compensation for the latter group was only 30 % of equally dramatic income fluctuations, greater need notwithstanding.