Severe spot lesions were shown to form on the surface of the liver in guinea pigs infected repeatedly with 2,500 embryonated eggs of the nematode Ascaris suum. The largest lesions measured 0.5 cm in diameter, and were hard in touch and white in color. Most of the lesions were classified macroscopically as compact lesions. Histopathologically, the lesions showed severe hemorrhage, massive necrotic foci, and eosinophilic infiltration in the liver. The findings in the livers of guinea pigs inoculated once only with Ascaris eggs (group D) were milder than those of animals that were infected repeatedly (group E). In contrast, the opposite was true for lesions in the lungs of guinea pigs belonging to these two groups.