When unexpected hemorrhage occurs during an operation, the neurovascular surgeon must immediately perform safe and secure hemostasis. Inappropriate hemostasis can lead to a circulatory disorder, cerebral edema, and hemorrhage. We describe safe and secure troubleshooting of different causes of hemorrhage, while presenting typical cases of cerebral aneurysm surgery. The following are discussed: 1. cerebral cortical vein 1) oozing, 2) small hemorrhage, 3) thick vein requiring reconstruction; 2. venous sinus 1) mild bleeding, 2) moderate bleeding, 3) severe bleeding; 3. bleeding from a lacerated aneurysmal neck; 4. new techniques using suction. Hemostasis with maintenance of normal structure was performed in all cases. The following are detailed methods used for each case. In 1.1) Gelfoam (Pfizer) soaked in saline was used; 1.2) minimum suturing was done; 1.3) frontal basal vein-radial vein-superficial middle cerebral vein anastomosis was performed. In 2.1) hemostatic material was used; 2.2) Goretex was placed over the bleeding site and covered with Gelfoam soaked in fibrin; 2.3) with sinus packing using neurosurgical pads for hemostasis, reconstruction of the sigmoid sinus using a saphenous venous patch was safely and quickly performed. In 3. the lacerated aneurysmal neck was repaired with 10-0 nylon interrupted sutures. Usual clipping based on closure line clipping was performed after securing hemostasis. In 4. in a narrow and deep operative field, use of the suction tip with the left hand enables cleaning of the bleeding point and self-sealing. Postoperative courses were uneventful and transfusion was not required. Appropriate troubleshooting without short-cuts is increasingly necessary because less invasive endovascular surgery can be easily performed.