OBJECTIVE: Permanent occlusion of an aneurysm with platinum coil embolization is achieved by thrombus formation and subsequent organization of the thrombus. However, these processes are often delayed or imcomplete. In this study, the authors present the effects of autologous fibroblasts-attached platinum coils on thrombus organization. METHODS: Experimental aneurysms were made on common carotid arteries bilaterally in four dogs. During the operation, dermal fibroblasts were obtained from the neck skin. The fibroblasts were attached on platinum coils by a simple co-culture for 5 days. In each animal, one aneurysm was embolized with autologous fibroblast-attached platinum coils(study group) and the other with plain platinum coils(control group). Two weeks later, the degree of intraaneurysmal thrombus organization was compared. RESULTS: The study group aneurysms showed more advanced organization than the control group(area occupied by organized thrombus / aneurysm cross sectional area = 79% vs. 54%, p=0.02). CONCLUSION: As a pilot study, this experiment demonstrates autologous fibroblast-attached platinum coils can facilitate permanent aneurysm obliteration. Autologous fibroblast-attached platinum coils may be used for the treatment of intracranial aneurysms.