Background: Cutaneous gnathostomiasis is an emerging food-borne parasitic zoonosis. Histopathological demonstration of the larva on random biopsy specimen of erythematous plaques is infrequent because of its migrating nature. Objective: We sought to determine whether medical treatment with albendazole or ivermectin increases the diagnostic yield of skin biopsy specimen. Methods: A retrospective chart review was conducted in a private dermatology practice in Lima, Peru. Cases with a clinical diagnosis of nodular migratory panniculitis and pathological diagnosis of eosinophilic panniculitis or gnathostomiasis were reviewed. Only cases with definitive diagnosis confirmed by histopathology or parasite isolation were included in the study. Results: A definitive diagnosis of gnathostomiasis was rendered in 6 of 55 reviewed cases. Histopathological or gross identification of the nematode's larva was made obtaining a biopsy specimen of papules or pseudofuruncles that developed after oral antiparasitic treatment. Limitations: This is a retrospective case series study and no serologic testing was available. Conclusion: Biopsy of a papule or pseudofuruncle subsequent to oral treatment increases the likelihood of demonstrating the larva on skin biopsy specimen, which allows definitive diagnosis and may have therapeutic benefit. © 2011 by the American Academy of Dermatology, Inc.