In clinical practice, occlusion of embolized, intracerebral aneurysms is evaluated using angiography. Standard, two-dimensional digital subtract angiography (DSA) is unable to quantify irregular aneurysm remnants, and even three-dimensional rotational angiography cannot quantify the degree of occlusion. To better understand occlusion at the aneurysm neck, we compared angiographic results with MICROFIL perfusion, histology, and scanning electron microscopy (SEM) results in 20 elastase-induced saccular aneurysms in rabbits. Aneurysms were embolized with HydroCoil devices (n = 12) or platinum coils (n = 8). Aneurysm follow-up occurred at 2 (n = 10) and 6 (n = 10) weeks. Aneurysm occlusion was evaluated using DSA, MICROFIL perfusion, histological ground sections, and SEM. Groups were compared statistically using ANOVA and chi(2) tests. The MICROFIL perfusion results were not concordant with the angiographic results for the HydroCoil and platinum coil groups. Both increased and decreased occlusion was observed on the MICROFIL-perfused aneurysms when compared with angiography. The histologic occlusion results of the HydroCoil group were concordant with the angiographic results; however, unoccluded areas not visible on angiography were routinely observed on the ground sections in the platinum coil group. SEM imaging of the aneurysm neck consistently showed decreased occlusion than angiographic results for both the HydroCoil and platinum coil groups. Although histology and MICROFIL-perfusion analyses provided additional details of aneurysm occlusion when compared with angiography, complete visualization of the entire neck of the aneurysm and accurate assessment of aneurysm occlusion was possible only with SEM.