The present study evaluated the pathogenicity of Baylisascaris potosis, a newly described ascarid nematode, in Mongolian gerbils. Gerbils were infected with varying doses of either B. potosis or Baylisascaris transfuga embryonated eggs (100, 1,000, and 4,000) for 30 days postinfection (pi). Baylisascaris potosis–infected gerbils showed no clinical signs of disease; however, gerbils exposed to 1,000 and 4,000 B. transfuga eggs showed severe neurologic signs at 22–29 days and 14–15 days pi, respectively. Histopathologic examination revealed larvae and lesions in the intestine, lung, liver, and muscles of B. potosis–infected gerbils, but not in the brain, whereas B. transfuga larvae were found only in the brain and muscle. These results indicate that B. potosis larvae migrate through numerous organs and are associated with visceral larva migrans in gerbils, but less frequently migrate to the nervous system in gerbils than does B. transfuga.