Arterial thrombo-embolectomy is often unsuccessful in those patients with acute limb ischaemia that have peripheral arteriosclerosis. During this study, conservative heparin treatment and, when needed, delayed surgery was employed in acute limb ischaemia when the ischaemia was less severe as judged by assessment of distal motor and sensory functions, regardless of the presumed aetiology of the acute ischaemia. The results are compared with those during a preceding period, when the routine treatment was emergency thrombo-embolectomy. The emergency operation rate was reduced to 49 per cent. There were overall fewer deaths with gangrene (8 per cent versus 18 per cent). In acute arterial thrombosis, more good results were obtained (76 per cent versus 47 per cent), whereas results were unchanged in embolic cases despite the reduced emergency operation rate. This study suggests that the choice of initial treatment of patients with acute limb ischaemia may be based on the severity of the ischaemia, and that patients with less severe acute ischaemia benefit from initial conservative heparin treatment.