Lifestyle interventions are effective for the prevention of type 2 diabetes in different populations with impaired glucose tolerance in the USA, 1 north Europe, 2 China, 3 and Japan. 4 Not only were the results impressive at the end of the intensive intervention trials, but long-term follow-up studies also confirmed the effect of lifestyle interventions for the prevention of diabetes in individuals at high risk of developing the disease. 2,3 Various drugs are efficacious in the prevention of type 2 diabetes in individuals with impaired glucose tolerance (figure). Glucose-lowering drugs preventedthe development of type 2 diabetes in placebo-controlled clinical trials. 1,3 Metformin reduced the relative risk of new-onset diabetes at the end of the US Diabetes Prevention Programme by 31%, 1 and a 26% reduction was seen inthe Indian Diabetes Prevention Programme. 8 Treatment with thiazolidinediones resulted in a greater risk reduction (60% with rosiglitazone in DREAM, 11 and 81% with pioglitazone in ACT-NOW 12-14 ). However, because both metformin and glitazones positively affect the pathophysiology of type 2 diabetes, 15 and because the main reported results were analysed without any washout period, the distinction between a masking and atrue preventive effect is almost impossible. 16 Another approach that would not directly affect insulin sensitivity or insulin secretion is to competitively inhibit intestinal α-glucosidase enzymes. 17 In the STOP-NIDDM trial, 6 done in Canada and various European countries, a 25% reduction was reported in the number of patients with new-onset diabetes and impaired glucose tolerance who were given acarbose (100 mg three times a day) compared with those given placebo after a 3-year followup. 6 Furthermore, acarbose significantly increased reversion of impaired glucose tolerance to normal. However, at the end of the study, treatment with placebo for 3 months was associated with an increase in conversion of impaired glucose tolerance to diabetes. Because acarbose does not interfere with the intestinal absorption of the monosaccharide glucose that is ingested during the oral glucose tolerance test, a masking effect seems unlikely compared with previous discussions about metformin or glitazones. 16 α-glucosidase inhibitors seem to exert a good glucose-lowering effect (with an acceptable gastrointestinal tolerance) in Asian people, presumably because of specific food habits. 18 Therefore the results of the trial by Kawamori and colleagues in The Lancet today, in which the effect of voglibose (another α-glucosidase inhibitor) was assessed in Japanese patients with impaired glucose tolerance, raise much interest. 5 Analysis after almost 50 weeks of treatment showed that voglibose (0 . 2 mg three times a day) reduced the risk of patients with impaired glucose tolerance developing type 2 diabetes by 40 . 5% and increased the proportion who achieved normoglycaemia by 53 . 9% compared with those given placebo. The underlying mechanism of action is not known. Unlike metformin and glitazones...