Pre-treatment selection of patients: Men and women, aged >50 years with peripheral arterial occlusive disease (Fontaine Stage II through IV) of one leg or both, unsuitable for surgical re-vascularisation, an ankle/brachial pressure index (ABPI) of <0.9 or a toe/brachial index of <0.7. Women must be surgically sterile or more than 2 years past their last menstrual period and test negative for pregnancy.