We did a population study to identify the prevalence of reactions to eight foods commonly perceived to cause sensitivity in the UK. A cross-sectional survey of 7500 households in the Wycombe Health Authority area and the same number of randomly-selected households nationwide was followed up by interviews of positive respondents from the Wycombe Health Authority area. Those who agreed entered a double-blind, placebo-controlled food challenge study to confirm food intolerance. 20.4% of the nationwide sample and 19.9% of the High Wycombe sample complained of food intolerance. Of the 93 subjects who entered the double-blind, placebo-controlled food challenge, 19.4% (95% confidence interval 11.4%-27.4%) had a positive reaction. The estimated prevalence of reactions to the eight foods tested in the population varied from 1.4% to 1.8% according to the definition used. Women perceived food intolerance more frequently and showed a higher rate of positive results to food challenge. There is a discrepancy between perception of food intolerance and the results of the double-blind placebo-controlled food challenges. The consequences of mistaken perception of food intolerance may be considerable in financial, nutritional, and health terms.