The application of chest US with triplex Doppler technique to detect the systemic feeding artery of lung sequestration in an adult patient is described. To our best knowledge, this is the first description of the use of this technique to diagnose pulmonary sequestration in adult patients. This 35-year-old man had necrotizing pneumonia with abscess formation at the left lower lobe. Chest US demonstrated a large tortuous vessel in the central part of the lesion. Spectral wave Doppler analysis showed that this vessel was a systemic feeding artery and had pulsatile arterial wave-form. The color Doppler mapping delineated the blood flow originating from the descending aorta and toward the lesion, thus confirming the diagnosis of pulmonary sequestration. We conclude that chest US with triplex Doppler technique is a valuable method in evaluating a patient with a pulmonary lesion who was thought to have lung sequestration before performing invasive aortography.