Acarbose is an alpha-glucosidase inhibitor which delays the absorption of glucose from the intestine. Taken orally before a meal, acarbose delays absorption of carbohydrates and decreases the postprandial plasma glucose and plasma insulin rise. A pilot study has been carried out to investigate whether acarbose can improve insulin sensitivity in subjects with impaired glucose tolerance (IGT). 18 subjects were randomized to receive either acarbose, 100 mg t.d.s., or placebo for 16 weeks. Acarbose therapy was found to decrease 2-hour plasma glucose and plasma insulin levels and to increase insulin sensitivity. Insulin resistance is an important factor in the development of non-insulin dependent diabetes mellitus (NIDDM).these results suggest that acarbose therapy may be able to prevent or delay the progression of IGT to NIDDM. A multicentre phase III clinical trial is now planned to investigate this possibility.