Dirofilariasis is an unusual but increasing cause of solitary pulmonary nodules. In this study, we reviewed the entire experience with dirofilariasis at our institution. Five such patients were identified. In all patients, the Dirofilaria immitis infection manifested as a solitary pulmonary nodule, and all patients underwent thoracotomy for diagnosis. None required systemic treatment. D. immitis is found in dog, cat, wolf, coyote, and fox populations throughout the United States, but the highest concentrations have been noted in the eastern, southeastern, and southern coastal states. The distribution of human cases of D. immitis infection has a similar pattern. Pulmonary dirofilariasis should be included in the differential diagnosis of peripheral noncalcified pulmonary nodules, especially in endemic areas.