In a 2002 telephone survey of 16,435 randomly selected U.S. residents, respondents answered several questions about their beliefs concerning sources of gastrointestinal illness. Of those who had experienced vomiting or diarrhea in the month before their telephone interview, 22% believed the source of their gastrointestinal illness was a meal eaten outside the home. Ill respondents who had diarrhea but not vomiting and who did not miss work because of their illness were more likely to believe the illness resulted from a specific outside meal. Ill respondents attributed their illness to a specific outside meal for several reasons, including symptom timing (43%) and illness of their meal companions (6%). Eight percent of ill respondents reported their illness to a health department or the restaurant suspected of causing the illness. Those with vomiting and those who missed work or activities because of their illness were more likely to report their illness. Most respondents (54%) who attributed their illness to a specific outside meal said their illness symptoms began within a short time (5 h) of eating that meal. The foodborne illnesses for which this is a likely time frame typically are associated with vomiting, but respondents with vomiting did not report a shorter symptom onset than respondents without vomiting. These findings suggest that ill respondents may have the misconception that foodborne illness symptoms typically occur shortly after ingestion of contaminated food. Results suggest that education efforts should focus on the nature and timing of foodborne illness symptoms and the importance of reporting suspected foodborne illnesses.