PURPOSE: Classically air in the portal vein has been detected on plain radiography, but computed tomography and ultrasonography have been shown to be more sensitive. We report a case of air in the PV in a 10-day-old infant with pneumatosis intestinalis with its ultrasonographic and Doppler findings. MATERIAL AND METHODS: The patient was a 10-day-old infant born by cesarean section at 41 weeks. Simple abdomen film revealed branching pattern of radiolucent air shadows within the contour of liver, gas distention of bowel loops and thickenod bowel walls with lincar intraluminal air shadows in abdomcn, suggesting neerotizing enterocolitis. So we performed Doppler ultrasonography. RESULTS: Ultrasonography showed branching pattern of hyperechogenic dots along the lumen of left portal vein. The color Doppler study revcaled an aliasing duo to increased velocity and whirling pattern of blood flow, and the Duplex Doppler spectral display showed sharp, vertical bidirectional spikes by air in portal vein. CONCLUSION: Air in the portal voin can be easily diagnosed by the followign signs:hyperechogenic dots in the portal vein on ultrasonography and vertical, sharp bidirectional spikes superimposod on the usual Doppler tracing of the portal vein on Duplex ultrasonography.