Object. Intracranial epidermoid cysts are rare. potentially curable. benign lesions that are sometimes associated with severe postoperative complications, including hemorrhage. Delayed hemorrhage. defined as one that Occurred after an initial unremarkable postoperative CT scan. contributed to most cases of postoperative hemorrhage in patients with epidermoid cyst. In this study, the authors focus on delayed hemorrhage as one of the severe postoperative complications in epidermoid cyst. report its incidence and its clinical features, and analyze related clinical parameters. Methods. There were 428 cases of intracranial epidermoid cysts that were surgically treated between 2002 and 2008 in Beijing Tiantan Hospital. and these were retrospectively reviewed. Among them, the cases with delayed postoperative hemorrhage were chosen for analysis. Clinical parameters were recorded. including the patient's age and sex, the chief surgeon's experience in neurosurgery. the year in which the operation was performed. tumor size. adhesion to neurovascular structures. and degree of resection. These parameters were compared in patients with and without delayed postoperative hemorrhage to identify risk factors associated with this entity. Results. The incidences of postoperative hemorrhage and delayed postoperative hemorrhage in patients with epidermoid cyst were 5.61% (24 of 428) and 4.91% (21 of 428), respectively, both of which were significantly higher than that of postoperative hemorrhage in all concurrently treated intracranial tumors. which was 0.91% (122 of 13.479). The onset of delayed postoperative hemorrhage ranged from the 5th to 23rd day at the operation: the median time of onset was the 8th day. The onset manifestation included signs of intracranial hypertension and/or meningeal irritation (71.4%). brain herniation (14.3%), seizures (9.5%). and syncope (4.8%). Neuroimages revealed hematoma in 11 cases and subarachnoid hemorrhage in 10 cases. The rehemorrhage rate was 38.1% (8 of 21). The mortality rate for delayed postoperative hemorrhage was 28.6% (6 of 21). None of the clinical parameters was correlated with delayed postoperative hemorrhage (p > 0.05). despite a relatively lower p value for adhesion to neurovascular structures (p = 0.096). Conclusions. Delayed postoperative hemorrhage contributed to most of the postoperative hemorrhages in patients with intracranial epidermoid cysts and was a unique postoperative complication with Unfavorable outcomes. Adhesion to neurovascular structures was possibly related to delayed postoperative hemorrhage (p = 0.096). (DOI: 10.3171/2010.12.JNS10325)