Forty-five patients with non-insulin-dependent diabetes mellitus (NIDDM) were enrolled in the study. Before and after the 2-week treatment course of oral erythromycin, esophageal (the mean transit time, MTT) and gastric motility (the halftime of gastric emptying, GETt1/2) were evaluated by radionuclide labeled liquid and solid meals. Meanwhile, the fasting blood sugar (FBS) levels were monitored. After a 2-week erythromycin treatment, MTT shortened from 9.32+/-1.12 to 6.28+/-0.91 s and GETt1/2 shortened from 210.2+/-24.3 to 128.3+/-30.1 min. Meanwhile, FBS decreased from 198.2+/-30.1 to 121.5+/-21.3 mg/dl (P value <.05). We conclude that a 2-week treatment course of oral erythromycin can significantly improve esophageal and gastric motility which results in a better control of blood sugar in patients with NIDDM.