Two unusual cases of iliac vein spontaneous rupture into the retroperitoneum are presented together with 18 cases reported by the literature. In one patient of ours, entrapment of clots in an IVC filter and proximal iliac vein involvement into the scar tissue surrounding the left limb of an aortoiliac bifurcation graft might have caused flow disturbances and subsequent predisposition to rupture of the thrombosed external iliac vein. Inflammatory parietal changes, including infiltration of macrophages, T and B lymphocytes producing elastin degradation by means of cytokines, may have led ultimately to vein disruption. Despite clinical features and CT scan findings, the physician's awareness of this disease remains the most important factor for the early treatment.