This paper analyses the story behind the implementation of the successful Chilean health policies by the National Health Service (NHS), between 1952 and 1973, a period distinguished by the expanded coverage of social benefits, the improvement of quality of life indicators and a tendency to universalise assistance among the Chilean population. The analysis has been centred on the work performed by social workers so as to examine an aspect that has been under-addressed by historiography about the State, a perspective that consists in exploring the performance of those bureaucracies in charge of implementing social policies, to discover the strains, contradictions and arrangements involved in building the State's actions, beyond its objectives and goals. As professionals in close contact with the people, social workers endured the burden of the everyday work around social policies, and contributed in legitimising the Service, as well as bringing out existing disputes among the health teams and the critical situation of the stiff bureaucratic structure.