Islet cell transplantation (ITx) can prevent serious recurrent hypoglycaemia. However, the components of hypoglycaemia unawareness usually ascribed to autonomic neuropathy can also be the result of Hypoglycaemia Associated Autonomic Failure (HAAF). This condition results from recurrent hypoglycaemia inhibiting the normal glucagon and sympatho-adrenal responses to low blood glucose levels. The mechanism resulting in the restoration of hypoglycaemia awareness post ITx have yet to be fully defined. The aim of this study was to measure restoration of hypoglycaemia awareness, in particular the contribution of HAAF, in the short term period post ITx. A total of 10 recipients (all female), aged between 42 and 62y (53.5±2.2y SEM), with longstanding type 1 diabetes (39.4±4.1y ) were studied. A composite hypoglycaemia score was documented using the Ryan Hypo Score method (glucose <3.0 mmol). We re-analysed the data to separately quantify: 1) the presence of autonomic symptoms & 2) the need for third party assistance. Major hypoglycaemia was virtually eliminated after ITx (40 episodes/month pre-ITx versus 2 episodes/month post-ITx. Total hypoglycaemic episodes per month fell from 145 pre-ITx to 11 at 0-6 months, and 5 at > 6 months. The percentage of hypoglycaemia episodes that had no autonomic symptoms fell from 97.5% to 48% at 0-6 months, and 26 % at > 6 months of follow up (all p<0.0001, Fisher's Exact Test). These results indicate that ITx in patients with Type 1 diabetes suffering from hypoglycaemia unawareness leads to significant restoration of autonomic symptoms associated with hypoglycaemia within 6 months. The rapid improvement observed suggests that HAAF is a major contributor to pre transplant hypoglycaemia unawareness.