Background and PurposeThe goal of the present study was to prospectively determine how frequently early growth of intracerebral hemorrhage occurs and whether this early growth is related to early neurological deterioration.MethodsWe performed a prospective observational study of patients with intracerebral hemorrhage within 3 hours of onset. Patients had a neurological evaluation and CT scan performed at baseline, 1 hour after baseline, and 20 hours after baseline.ResultsSubstantial growth in the volume of parenchymal hemorrhage occurred in 26% of the 103 study patients between the baseline and 1-hour CT scans. An additional 12% of patients had substantial growth between the 1- and 20-hour CT scans. Hemorrhage growth between the baseline and 1-hour CT scans was significantly associated with clinical deterioration, as measured by the change between the baseline and 1-hour Glasgow Coma Scale and National Institutes of Health Stroke Scale scores. No baseline clinical or CT prediction of hemorrhage growth was identified.ConclusionsSubstantial early hemorrhage growth in patients with intracerebral hemorrhage is common and is associated with neurological deterioration. Randomized treatment trials are needed to determine whether this early natural history of ongoing bleeding and frequent neurological deterioration can be improved. (Stroke. 1997;28:1-5.)