OBJECTIVE The prognosis of giant aneurysms remains poor despite recent advances in microneurosurgery. Thick-walled and partially calcified giant aneurysms with an atheromatic base are difficult to clip safely. Special techniques allowing reshaping of the base and ensuring the stability of clips are often needed. We present our experience with direct clipping of thick-walled giant aneurysms with the aid of the DeBakey cardiovascular clamp (Aesculap, Tuttlingen, Germany). METHODS Eighty-two patients with a giant aneurysm (>/=25 mm) were treated actively at the Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland, between 1997 and 2007. The vascular clamp technique was used in 8 of 50 patients in whom direct clipping was performed. The remaining patients were treated with bypass and trapping, trapping only, proximal occlusion, coiling, or explorative surgery. RESULTS The vascular clamp (DeBakey in 5 cases, Crile forceps [Medicon Medizin-Technik, Tuttlingen, Germany] in 2 cases, and Halsted-Mosquito forceps [Medicon Medizin-Technik, Tuttlingen, Germany] in 1 case) was used in 7 saccular middle cerebral artery aneurysms and 1 fusiform basilar bifurcation aneurysm. Two patients had postoperative infarctions, 1 attributable to occlusion of perforators by a clip and the other caused by clips sliding down the calcified base, occluding a major branch. Six patients had no neurological sequelae, 1 patient had transient upper limb paresis, and the patient with the occluded major branch died. CONCLUSION The DeBakey vascular clamp is helpful in assisting direct clipping of thick-walled giant aneurysms with a partially calcified atheromatic base. Some practical features of this instrument require further refinement.