Electrolytic detachable coils （EDC） have been the main embolic materi als for intracranial aneurysms. Liquid aneurysmal embolic materials represented by cellulose acetate polymer （CAP） are still in controversy. In this research

t he embolization results and pathological reactions after embolization of canine aneurysmal models with EDC or CAP were observed and compared. Methods. The canine aneurysmal models constructed by anastomosis of venous pouch es were randomly grouped. The aneurysms were respectively occluded with CAP and electrolytic detachable coils that was named by Wu electrolytic detachable coil （WEDC） and made by us. Angiogram follow ups were performed at 24 hour

2 week

and 2 month after embolization. The occluded aneurysms were dissected in each stage for light microscopic

electron microscopic

and histochemical research. Results. The effect of embolization was significantly better with WEDC than that with CAP . Post embolized complications such as aneurysm rupture and stenosis of parent arteries could only be found in CAP group. Pathol ogical research showed that CAP mass could packed the aneurysms more densely tha n coils. Acute chemical damage of aneurysmal wall and inflammatory cell infiltra tion was prominently found in early stage after CAP embolization. Organization of thrombus inside aneurysms and formation of endothelial tissue over the orific es of aneurysmal necks could be found in both groups 2 months after embolization . But parts of coils might be exposed outside endothelial layer. Conclusions. EDC are still the most safe

efficient

and reliable instruments to embolize aneurysm. CAP should be improved further to solve the problem of stron g chemical corrosion and difficulty in control before it is widely used.