Conditions in institutions for children or defectives may become peculiarly favourable to the propagation of hookworm disease. The subject of the present study is a long-standing infection with Ancylostoma duodenale in the Hospital for the Insane at Goodna, Queensland, the largest of the three hospitals for the insane maintained by the State Government. The investigation was of special interest because the institution is in a region in which the general population is free from hookworm disease, owing to low rainfall, and because the infection was with A. duodenale, while the predominating hookworm infection of Queensland is with Necator americanus.