Acarbose is the first of a new class of oral antidiabetic agents, the α-glucosidase inhibitors. Although the efficacy and safety of acarbose in hyperglycemic control subjects have been thoroughly demonstrated, approximately 50% or more of acarbose-treated subjects in recent clinical trials reported adverse gastrointestinal effects. Acarbose causes delayed absorption of carbohydrates from the intestine, providing a substrate for fermentation by colonic flora. Although these effects are not serious and are known to diminish over time, patients in general clinical practice may not be adequately informed of this fact or as motivated as trial subjects to persist with the therapy, and hence may prematurely discontinue use of the agent. This cohort study assesses adverse effects with acarbose treatment among new users of the drug. Forty percent of patients aged 21 to 64 years and 35% of senior citizens failed to renew their first dispensed prescription within a permissible period. Predictors of early discontinuation were identified and discussed. This study underscores the importance of the role of prescribing practitioners in educating patients receiving acarbose treatment about the anticipated gastrointestinal adverse effects and their expected diminution over time. Such education may improve compliance and prevent the waste of health care resources.