Between the years 1921 and 1938, 27 600 children were irradiated during a mass campaign to eradicate ringworm among the Jewish community in East Europe. The ringworm campaign was the initiative of the American Jewish Joint Distribution Committee together with the Jewish health maintenance organization OZE (The Society for the Protection of Jewish Health). We describe this campaign that used x-rays to eradicate ringworm and its mission to enhance public health among Jewish communities in Eastern Europe during the period between the world wars. We discuss the concepts behind the campaign, the primary health agents that participated in it, and the latent medical ramifications that were found among children treated for ringworm, many years after treatment-pathologies that can be linked to the irradiation they received as children. Our research is based on historical archival materials in the United States, Europe, and Israel.