Twelve newborn infants with clinical evidence of hypoxic ischemic brain injury had conventional and diffusion-weighted magnetic resonance imaging (MRI) performed one to six (median two) days and 7-42 days after birth. The extent and conspicuity of the early abnormalities was greater with diffusion-weighted than with conventional imaging in each of the four infants with neonatal infarction and in four of the infants with Grades II or III hypoxic ischemic encephalopathy (HIE). No abnormality was seen with either technique in the other four infants who had Grades I or II HIE. Diffusion weighted MRI may be important for the early diagnosis and grading of infants with hypoxic ischemic brain injury.