This article explores the first international effort by the League of Nations Health Organization (LNHO) to standardize the study of the effects of the economic crisis of the 1930s on health. Instead of analysing this effort with the benefit of hindsight, this article takes into account the actors' perspectives and, therefore, it relies on the documents produced by the LNHO and public health experts of the 1930s, as well as on the historical scholarship on this subject. This article shows that, despite the declining death rates in Europe and in the US during the crisis, the LNHO considered that death rates concealed a more subtle effect of the crisis on health; hence, they launched a project aimed at making the effect visible. It describes the LNHO programme and the guidelines and methods set out by the organization in 1932 to observe this subtle effect through sociomedical investigations. The results of these surveys are summarized and the article discusses how the eugenic arguments used to explain them were not accepted by the LNHO. The article also shows how some members of the LNHO considered the results of the sociomedical surveys inconclusive and questioned the usefulness of socioeconomic indicators; in so doing, they raised concerns about the intervention of the LNHO in national matters and about the risks of crossing the established limits between science and politics. This article shows that an historical analysis, which takes into account the points of view of the actors involved, illuminates the factors that led the LNHO to conclude that mortality rates were the best method for measuring the effects of the economic crisis on health and that, as they were declining, the Great Depression was not having any deleterious effect on public health.