Obligatory insurance was introduced in Spain in the 1940s. Until that time, a high percentage of workers and their families entrusted healthcare to the Mutual Assistance Societies, Mutual Insurance Associations and other private institutions. For this reason, analysis of the assistance offered by these organizations during ill health is of interest.

Mutual benefit societies were voluntary associations whose members participated in management and administration. Profits belonged to the members as a whole and were distributed following statutes or regulations. In general, these organizations were classified following the ideological inspiration of their sponsors and their social composition. In the first third of the twentieth century there were numerous mutual benefit societies in Spain, which gave social and heath care to much of the population.

The interest in the study of mutualism and its evolution with reference to the introduction of Obligatory Heath Insurance and the National Health has been underlined. Particularly in Spain, the meagre budget provided for the Instituto Nacional de Previsión (INP) from its creation (1908) was the reason for reliance on the Mutual Benefit Societies and other private associations to organize precautionary measures for workers and their families.

The evolution of the system and identity of a Mutual Benefit Society: the ‘Sociedad Protectora de Obreros La Conciliación’ from its beginning in 1902 until 1984, reflects the medical-social reforms carried out in the country during this period, and provides us with an opportune viewing point for understanding the complexity of the introduction of the Social Security system.