The angiographic changes in neck remnants of ruptured cerebral aneurysms treated with Guglielmi detachable coils (GDCs) were evaluated in the acute stage to analyze the important radiological and clinical factors. The clinical and radiological data of 37 patients with a residual neck of a ruptured cerebral aneurysm treated with GDC were reviewed. The angiographic changes on follow-up angiography were classified into three groups: recanalization of the neck remnant, progressive thrombosis, and unchanged. The effects of the clinical and angiographic findings, such as patient age, follow-up period, type of aneurysm (terminal type or side wall type), dome diameter, neck size, dome/neck ratio, obliteration rate, and volume embolization ratio were investigated. Recanalization of the neck remnant was observed in 18 of 37 cases, progressive thrombosis in nine, and unchanged in 10. The type of aneurysm, dome diameter, neck size, and volume embolization ratio were correlated with changes in the neck remnant. The aneurysm dome diameter and type of aneurysm were independent predictive factors for the recanalization of neck remnants on follow-up angiography. Dome diameter of less than 4.5 mm and volume embolization ratio of more than 31% in side wall aneurysms were likely to lead to progressive thrombosis.