Nine patients underwent transcatheter embolization with a suspension of microfibrillar collagen hemostat (MCH). Four of the patients had large vascular renal tumors, and two had bleeding bladder carcinomas. There was one case each of bleeding rectal tumor, bleeding esophageal varices, and arteriovenous malformation of the shoulder. MCH was highly thrombogenic and could be injected through very small catheters. It was highly effective as an occlusive agent and was able to penetrate the small end-arteries of a lesion. Its main disadvantage is that if normal tissues are inadvertently embolized, there is a risk of ischemic complication.