Metoclopramide tablets have been approved for use in the acute and chronic management of diabetic gastroparesis. Its efficacy as an antiemetic has been well documented. We measured the acute and chronic effects of oral metoclopramide on gastric liquid emptying in 12 diabetic patients with symptoms of stasis using scintiscanning techniques. We found that liquid emptying in these subjects was abnormal, as determined by residue area determination when compared to normal volunteers (P less than 0.01). Metoclopramide 10 mg orally acutely enhanced emptying, restoring it to control values (P less than 0.01). In contrast, when gastric emptying was evaluated following one month of chronic liquid metoclopramide use, 10 mg before each meal, the acute effect of the drug on emptying could no longer be demonstrated and residue areas returned to baseline values, suggesting that chronic oral administration of metoclopramide may result in a loss of the gastrokinetic properties of this drug.