OBJECTIVE To evaluate the safety and effectiveness of superselective coil embolization with coaxial microballoon occlusion (B-coiling) for vascular disorders. METHODS Clinical data were retrospectively evaluated for 16 consecutive patients (6 men, 10 women; mean age, 70 y; age range, 57-80 y) with vascular disorders who underwent B-coiling with 0.010-0.014-inch detachable microcoils delivered through a guide-wire lumen of a microballoon catheter. Routine angiographic catheters (4-5 F) were introduced in all cases, including splenic (n = 4) and renal (n = 3) artery aneurysms, pulmonary and renal arteriovenous malformations (AVMs; n = 3 and n = 1, respectively), gastroesophageal varices (GEVs; n = 3), gastroduodenal artery stump pseudoaneurysm (n = 1), and superficial temporal artery aneurysm (n = 1). RESULTS Complete primary occlusion was achieved in 87.5% of cases (n = 14) without complications. Additional percutaneous transhepatic sclerotherapy by N-butyl cyanoacrylate (NBCA)/iodized oil mixtures without balloon occlusion resulted in successful occlusion of one GEV. Additional balloon-occluded NBCA injection was successfully performed in one renal AVM. CONCLUSIONS Superselective coaxial microballoon embolization with detachable microcoils is a safe and useful treatment. Selective B-coiling induces tight packing under flow control in the treatment of vascular disorders.