Computed tomography (CT) scan is the most accurate method for diagnosing intracerebral hemorrhage in the high-risk preterm infant. The present study was undertaken to evaluate lumbar puncture (LP) as a reliable means of diagnosing such hemorrhages. Forty eight infants less than 35 weeks gestation, requiring intensive care, were evaluated by CT scan at 48 to 96 hours of life, and serial LPs were performed. The initial LP preceded the CT scan by one to four hours and repeat LPs were done three and five days later if the initial CT scan revealed intracerebral hemorrhage. The initial LP was successfully performed in 28 of 48 infants. Of these 48 infants, 15 had hemorrhage by CT scan. The initial LP was consistent with the diagnosis on scan in eight of these 15. In the other seven infants, initial LP was normal in three, traumatic in one, and unsuccessful in three. The second LP was consistent with hemorrhage in four of the latter seven. Thus, in only eight of 15 infants, in whom CT scans revealed intracerebral hemorrhage, was the initial LP useful in confirming the diagnosis. Furthermore, LPs showed bloody cerebrospinal fluid in 10 of 18 infants whose CT scans were normal. At the present time LP cannot be considered a reliable means of identifying infants with subependymal-intraventricular hemorrhage.