The authors found that aneurysm rebleeding after subarachnoid hemorrhage (SAH) has specific characteristics in the preoperative, intraoperative, and postoperative periods, involving aneurysm size, heart disease, aneurysm location, family history, clipping, coiling, etc.According to Horie and colleagues, their study is the first to assess the characteristics and predictors of aneurysmal SAH rebleeding in the preoperative, intraoperative, and postoperative periods.We would like to express our respect for their achievements and to share some comments with the authors.Firstly, and most importantly, the data were collected from 1 university hospital and 10 affiliated hospitals.The authors did not consider the role of these medical institutions in their analysis.Depending on the different medical levels of doctors in these hospitals, different degrees of surgical instruments and equipment, and different management methods after operation, these factors could affect the probability of aneurysm rupture during and after surgery.Therefore, it is difficult to control bias in data collected from 11 hospitals.Secondly, their article does not provide inclusion criteria for the study subjects but simply describes exclusion criteria.It only rules out subjects younger than 18 years of age and nonaneurysmal SAH including dissection.