Objective: The purpose of this survey was to establish a database of habitual food and drink consumption in a representative sample of Irish adults aged 18-64 years. Design: A cross-sectional food consumption survey was carried out. Food intake data were collected using a 7-day estimated food diary. Anthropometric data included measurements of weight, height, waist and hip circumferences and body composition using bioelectrical impedance analysis. Questionnaire data included assessments of health, lifestyle and socio-demographic status, levels of physical activity, attitudes to diet and health and restrained eating. Setting: Northern Ireland and Republic of Ireland between 1997 and 1999. Results: In total, 1379 adults aged 18-64 years participated in the survey and completed the 7-day food diary. This paper gives details of the methods used to carry out the survey. Sampling, respondent recruitment, dietary assessment, collection of anthropometric and questionnaire data and data management and analysis are described. Conclusion: The North/South Ireland Food Consumption Survey is unique in being the first food consumption survey ever to be carried out in the Republic of Ireland and Northern Ireland concurrently using the same methodology.