Type II endoleaks after endovascular aneurysm repair are the most common type of endoleak and generate the majority of secondary interventions. Their natural history is mostly benign, but they can occasionally lead to sac expansion and eventual rupture. Three-phase computed tomography angiography is the "gold standard" for diagnosis, but duplex ultrasound with or without contrast enhancement and magnetic resonance angiography offer an alternative for endoleak detection or surveillance. Whereas there are concerns as to whether sac expansion can be a dependable marker for risk of rupture, it is currently the best surrogate available and guides the indication for intervention. Obliteration of type II endoleaks can be challenging, and a variety of techniques, endovascular, open, and laparoscopic, have been proposed. The most common approaches are transarterial and translumbar embolization, and they are usually successful, provided the operator is experienced and persistent, targeting both the branches and the nidus of the endoleak. Recurrences and subsequent reinterventions should be anticipated, and on continuing sac expansion, repeated endovascular or open surgical and laparoscopic alternatives may be required.