Between July, 2006, and October, 2010, ten cases of Paragonimus were identified among persons who had eaten raw crayfish harvested from Missouri rivers. Delayed diagnosis and severe illness were common. Illness symptoms consisted of fever, cough, pleural effusion (fluid accumulation around the lungs), and eosinophilia (increase in white blood cells that suggest an infection with a parasite). All cases recovered when they were treated with praziquantel, a medication. During 1965--2007, only six other cases of non-imported paragonimiasis were reported in the United States, occurring in Colorado, Iowa, Michigan, Missouri, and Oklahoma. Among those six patients, five had eaten crayfish. The life cycle of P. kellicotti requires two intermediate hosts. The first intermediate host is a snail (e.g., Pomatiopsis lapidaria), and the second is crayfish, principally Cambarus spp. (1). After humans eat raw or undercooked crayfish that harbor P. kellicotti, the parasite penetrates through the intestinal wall into the peritoneal cavity, then through the diaphragm into the pleural space and lungs, and can migrate to other organs, including the brain and skin. Eggs laid in lungs are excreted in sputum, or swallowed and passed with stool. Paragonimus are present in Africa, the Americas, and Asia, but the distribution of P. kellicotti is not completely defined.