The pseudoaneurysms are resulted from complication of vascular catheterization, trauma, etc. and recently, the reports on pseudoaneurysms have been increasing. Successful treatment of pseudoaneurysms have been described usingdirect compression guided by color doppler ultrasound, instead of invasive surgical treatment. Authors experienced three cases of pseudoaneurysm ; two resulted from post-catheterization and one from trauma. We successfully treated two post-catheterization cases using C-clamp compression under the color doppler US-guidance. The traumatic case was treated by embolization instead of US-guided compression. We suggest that the compression of pseudoaneurysm using C-clamp under the US-guidance is more useful than hand or probe compression method.