BACKGROUND Abnormal gastrointestinal motility is a well recognized complication of diabetes mellitus, and disordered gastric emptying may hamper glycemic control. The objects of this study were to investigate the effect of oral erythromycin on gastric emptying and to evaluate the effect of corrected gastric emptying on glycemic control in patients with diabetic gastroparesis. METHODS Twenty patients of Type II (non-insulin-dependent) diabetes mellitus with typical symptoms of gastroparesis and delayed solid phase gastric emptying were studied. There were 18 males and 2 females, aged 49 to 72 years. Erythromycin (erythromycin estolate) was given orally at a dose of 250 mg, 3 times daily, 30 minutes before each meal. Radionuclide-labelled solid phase gastric emptying and fasting blood sugar (FBS) were studied after one day of erythromycin therapy, and again after 2 weeks of the therapy. The half time of gastric emptying (GETt1/2) represented the time needed for 50 percent of the initial radioactivity to leave the stomach, and was used to express the gastric emptying status. RESULTS The GETt1/2 decreased from 198.0 +/- 58.9 minutes at baseline to 139.1 +/- 67.6 minutes following one day of erythromycin therapy (p < 0.01), and to 137.1 +/- 71.2 minutes after two weeks of treatment (vs. baseline p < 0.01). The FBS decreased from 159.0 +/- 40.2 mg/dl at baseline to 149.0 +/- 38.5 mg/dl following one day of therapy (p = 0.12, NS), and to 139.2 +/- 39.8 mg/dl after two weeks of treatment (vs. baseline p < 0.02). CONCLUSIONS It was concluded that erythromycin is an effective prokinetic agent for diabetic gastroparesis, and that corrected gastric emptying may improve glycemic control.