Sixteen patients with 22 isolated aneurysms of the common or external iliac artery were treated between 1974 and 1986. There were ten men and six women with a median age of 69 years. The aneurysm was discovered incidentally in seven patients; and in nine patients it was diagnosed upon rupture. A pulsating abdominal tumour was palpable in 12 patients seven of whom had a ruptured aneurysm. Common symptoms included urological and neurological problems and abdominal pain. Of the seven patients in whom the diagnosis was confirmed prior to rupture, three were operated upon successfully and four were not. Of the latter, two died within 3 months due to coexisting disease while two remain alive after one and 6 years. Of the nine patients with a ruptured aneurysm only four survived. The high risk of rupture justifies elective operation of an aneurysm of the iliac artery in the majority of cases.