In 10 patients with Type 1 (insulin-dependent) diabetes mellitus gastric emptying of a digestible solid and liquid meal was measured during euglycaemia (blood glucose concentration 4-8 mmol/l) and during hyperglycaemia (blood glucose concentration 16-20 mmol/l). Gastric emptying was studied with a scintigraphic technique and blood glucose concentrations were stabilised using a modified glucose clamp. Patients were also evaluated for gastrointestinal symptoms, autonomic nerve function and glycaemic control. When compared to euglycaemia, the duration of the lag phase before any of the solid meal emptied from the stomach (p = 0.032), the percentage of the solid meal remaining in the stomach at 100 min (p = 0.032) and the 50% emptying time for the solid meal (p = 0.032) increased during hyperglycaemia. The 50% emptying time for the liquid meal (p = 0.042) was also prolonged during the period of hyperglycaemia. These results demonstrate that the rate of gastric emptying in Type 1 diabetes is affected by the blood glucose concentration.