A paleoparasitological study was performed on soil samples obtained at archaeological sites dating to the Baekje period in ancient Korean history. The samples were obtained from Buyeo, the capital area of the Baekje Kingdom, and from others corresponding to provincial counties of the same period. We found Ascaris lumbricoides and Trichuris trichiura eggs in the Buyeo samples but not any in the samples from the provincial counties. Our results suggest that the parasite-egg contamination patterns were closely correlated with population densities, in that the provincial counties of the Kingdom, compared with the capital Buyeo, were very sparsely populated. This is the first comprehensive paleoparasitological report on soil contamination patterns in the capital of the Baekje Kingdom, one of the most highly populated areas in ancient Korean history.