Recent studies on parasite eggs uncovered at archaeological sites have yielded an abundance of scientific evidence that enhances the understanding of historical infection patterns in Korea and East Asia in general. Rescue archaeology conducted in Hansŏng, the capital area of the Chosŏn dynasty in Seoul Metropolitan City, has been especially revelatory of the serious extent to which the inhabitants were infected with soil-transmitted parasites. Chosŏn historical documents have prompted reinterpretations of our paleoparasitological results, affording a vivid glimpse of the Hansŏng inhabitants’ sanitary status. We speculate that parasitism among the Chosŏn people was significantly influenced by the economic interdependence between major cities and nearby farmlands, whose relationship was common in seventeenth–nineteenth-century East Asia. Since the night soil produced in a major city was recycled by farmers as fertilizer for vegetables, soil-transmitted parasitism must have been prevalent among the city-dwellers of the Chosŏn period. A high level of infection was a kind of unavoidable by-product of the night soil recycling process, which otherwise was very efficacious for the sustainable management of a pre-industrialized city in Korea.