Objective: To obtain measured anthropometric data for weight, height and other parameters not previously measured in the Irish population such as waist and hip circumferences and body composition. Design: A cross-sectional survey. Weight, height, waist circumference, hip circumference and body composition were measured according to standard procedures. Setting: Northern Ireland and the Republic of Ireland, 1997-1999. Subjects: Random representative sample of 1379 adults aged 18-64 years. Results: With the exception of body fiat, all anthropometric values were significantly higher for men than women (P < 0.001). All measurements were significantly higher in the 36-50-year-old age group compared with 18-35 year olds. Height was the exception, which decreased significantly with age (P < 0.05). Weight, height and body mass index (BMI) have increased in Ireland Since last measured in 1988 and in 1990. Over the last decade, obesity has increased in men 2.5 fold from 8% to 20% and in women by 1.25 fold from 13% to 16%. Significantly more women have a normal BMI than men (50.4% vs. 33.3%; P < 0.05). Cut-off points for a high waist circumference and high waist-to-hip ratio identified 47% and 33% of the population, respectively, to be at an increased risk for cardiovascular disease. Social class did not have any significant effect on mean BMI. Location of residence influenced BMI but not in any consistent manner. Ex-smokers had a significantly higher BMI than nonsmokers and smokers (P < 0.05). Conclusions: A revision of current recommendations for combating obesity is warranted to improve the health of the Irish population, Further research is needed to identify the factors that have contributed to the dramatic increase in the prevalence of obesity in men over the last decade and have resulted in a higher prevalence of obesity in men than in women.