1. A questionnaire inquiring about food intolerance was sent to a random sample of the electorate in a small South Wales town. Replies were received from 170 men and 305 women, the response rates being 87 and 93% respectively. 2. Adverse effects of some food were reported by 19% of men and 26% of women, or 14 and 18% respectively if minor digestive symptoms are excluded. Certain foods were thought to cause non-abdominal symptoms by 4% of men and 10% of women, and vomiting, diarrhoea or abdominal pain by 11% of men and 10% of women. 3. Plasma IgE was measured in a random subset of ninety-nine women and found to be significantly lower in those with major symptoms than in the rest. This suggests that allergy is probably not a common cause of food intolerance.