Objective: To study the clinical and neuroimaging predictors of hematoma enlargement in spontaneous intracerebral hemorrhage (ICH). Methods: Ninety-eight patients with ICH within 4 hours of onset, 60 males and 38 females, aged 56 ± 16, underwent the first CT examination at admission and the second CT examination 24 hours later to evaluate the occurrence of hematoma enlargement. Multivariate analysis was performed to assess the possible predictors. Results: Twenty-six of the 98 ICH patients (26.5%) developed hematoma enlargement. Multivariate analysis revealed that the following 4 factors were independently associated with hematoma enlargement: interval between first CT and onset, aniso-density hematoma, consciousness level at admission, and the history of cerebral infarction. A characteristic feature indicating the hematoma enlargement- "hematoma enlargement border" was found and named. Conclusion: Hematoma enlargement after ICH has some clinical and neuroimaging predictors. The concepts and diagnostic criteria of aniso-density hematoma and hematoma enlargement border have been defined for the first time.