BACKGROUND/AIMS: The prevalence of diagnosed gastroparesis is 24.2/100,000 inhabitants, but a large group of people with gastroparesis-like symptoms have never had a gastric emptying (GE) test. Some of them may have undiagnosed gastroparesis. Our aim was to estimate the prevalence of hidden gastroparesis in the community. METHODS: The study was conducted in 2 parts: (1) Patients referred for a scintigraphic GE test completed a validated questionnaire (Bowel Disease Questionnaire). Multiple linear regression models to predict 2 hours and 4 hours GE rates were developed. (2) A revised Bowel Disease Questionnaire was mailed to a random sample of 4,194 Olmsted County residents. GE rates were estimated with the models for each subject and delayed GE was considered when they were lower than normal values. Hidden gastroparesis was defined in community subjects with predicted delayed GE that had not been diagnosed with gastroparesis prior to the survey. RESULTS: The regression models for GE rates were constructed using data from 450 patients. In addition to age and gender, the symptoms found significant were nausea/vomiting, early satiety, upper abdominal pain, bloating, loss of appetite and weight loss more than 7 pounds. 2,298 (55%) community subjects returned a questionnaire. Five subjects were excluded due to a prior diagnosis of gastroparesis. When models were applied to the community survey data, 42 (1.8%) subjects were estimated to have delayed GE. CONCLUSIONS: Delayed GE was estimated to occur in 1.8% of community subjects. Since the prevalence of diagnosed gastroparesis is low (0.02%), many subjects with gastroparesis may remain undiagnosed.