One worm recovered from the orbit of a patient in Indiana, and two from the peritoneal cavity of another patient in California are described and classified as Dirofilaria. Both patients were elderly men who have lived all their lives in the United States. The main morphologic feature of these three immature worms is the presence of a smooth cuticle devoid of longitudinal ridges, similar to the cuticle of D. immitis. However, because other dirofilariid with similar cuticular characteristics have been found in animals in the Western Hemisphere, and they cannot be conclusively ruled out as the cause of the infection in our patients, a diagnosis of D. immitis-like organism is proposed for these nematodes. The relationship of these worms to other dirofilariid of animals and humans on the American continent is important because of the diagnostic problems these infections posed to practicing pathologists.