This study ascertained the prevalence of severe hypoglycaemia and loss of awareness of hypoglycaemia in patients with Type 2 diabetes treated with insulin. One hundred and four sequentially selected Type 2 diabetic patients were compared with 104 patients with Type 1 diabetes who were matched for duration of insulin therapy. The patients were interviewed using a standardized questionnaire. During treatment with insulin, 18 Type 2 patients had experienced fewer than two episodes of hypoglycaemia, while 86 had experienced two or more episodes; 80 (93%) reported normal awareness, six (7%) reported partial awareness, and none had absent awareness of hypoglycaemia. All 86 Type 1 diabetic patients matched to the 86 Type 2 patients had experienced multiple episodes of hypoglycaemia; 71 (83%) had normal awareness, 14 (16%) had partial awareness and one patient (1%) reported absent awareness of hypoglycaemia. The Type 1 patients who had altered awareness of hypoglycaemia had longer duration of diabetes and insulin therapy (normal awareness: 5 (1-17) years (median (range)) vs partial awareness: 9 (3-18) years, p < 0.01). Similarly, Type 2 patients with altered awareness had longer duration of diabetes (normal awareness: 11 (2-25) years vs partial awareness: 19 (8-24) years, p < 0.02) and had received insulin for longer (normal awareness: 3 (1-18) years vs partial awareness: 12 (6-17) years, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)