Background: The prevalence of diabetic gastroparesis is not well defined because of discrepancy between objective measurements, i.e. gastric emptying time, and symptoms experienced by patients. Furthermore most studies have been performed on small selected cohorts. Objective: To determine the prevalence of clinical symptoms of diabetic gastroparesis in a large unselected cohort of out-patients with Type 1 diabetes. Methods: 1028 patients with Type 1 diabetes attending a specialized diabetes clinic were mailed a validated questionnaire; "patient assessment of upper gastrointestinal disorders-symptom severity index", in which a subset of questions measures symptoms of gastroparesis (GCSI; Gastroparesis Cardinal Symptom Index). Response rate was 74.4% (n = 765). All patients were classified according to presence or absence of late diabetic complications and clinical and paraclinical data were obtained. Results: A GCSI Total Score ≥ 1.90 signified definite symptoms of gastroparesis (n = 102) and patient charts were investigated for concomitant illness and/or medication influencing gastric emptying. In 30 patients an alternative etiology was revealed, leaving 72 (9.8%) patients with symptoms related to diabetic gastroparesis. Only 8 patients were previously diagnosed. HbA 1c levels were significantly higher in patients with diabetic gastroparesis (8.4 ± 1.3 vs. 8.2 ± 1.2 respectively, p = 0.02). Furthermore, patients with diabetic gastroparesis had more retinopathy (p = 0.006) and peripheral polyneuropathy (16.7% vs. 6.7%, p < 0.001) and there was a trend for diabetic nephropathy being more common (p = 0.08). Conclusions: Symptoms of diabetic gastroparesis affect approximately 10% of patients with Type 1 diabetes in a specialized diabetes clinic and are associated with poor glycemic control and other late diabetic complications.