We examine the efforts of the International Labour Organisation (ILO) to extend medical care under social security, through international conventions, advocacy and technical assistance. We consider the challenges faced by the ILO in advancing global health coverage through its labourist, social security model. The narrative begins in the interwar period, with the early conventions on sickness insurance, then discusses the rights-based universalistic vision expressed in the Philadelphia Declaration (1944). We characterize the ILO's postwar research and technical assistance as "progressive gradualism" then show how from the late-1970s the ILO became increasingly marginalized, though it retained an advisory role within the now dominant "co-operative pluralistic" model.