Using a validated postal questionnaire, we investigated the frequency of 24 gastrointestinal symptoms during the previous 3 months in a cohort of 110 young adult patients (54 males and 56 females, mean age 37.2 +/- 4.7 years) with onset of Type 1 diabetes mellitus at < 16 years of age. They were compared with 210 age- and sex-matched controls (104 males and 106 females). The main difference in the frequency of various symptoms between the two groups was a significant increase among the diabetic patients in upper gastrointestinal symptoms, such as loss of appetite (17.8% vs 3.6%, p < 0.001), early satiety (26.8% vs 6.1%, p < 0.001), nausea (22.7% vs 9.1%, p < 0.01) and vomiting (12.2% vs 3.0%, p < 0.01). No difference was noted in the frequency of symptoms from the lower gastrointestinal tract, apart from a significant increase in the feeling of incomplete defaecation (28.6% vs 17.0%, p < 0.04) in the diabetic patients. Patients with levels of haemoglobin A1c in the highest quartile had significantly more gastrointestinal symptoms than other diabetic patients. Further, the prevalence of symptoms was higher in females than in males. In conclusion, long-term Type 1 diabetes is accompanied by a markedly increased frequency of upper gastrointestinal symptoms, mainly in females and patients with poor metabolic control.