The purpose of the study was: (1) to estimate body fat and body fat distribution in the general population of Danes aged 35-65 years and thus provide tables of normal values for adult Danes in these age groups; and (2) to assess the effects of age and gender on relations between measures of obesity and of fat distribution. Hitherto, the only available results from the Danish population have been on BMI. Of the 3608 invited subjects 2987 (83 per cent) attended the examination. Body fat and fat distribution were estimated from measurements of electrical impedance and from circumference measurements. The study showed large differences in body fat and fat distribution between men and women. There was a difference in total body fat of 4.5 and 6.9 kg in men and women respectively between the groups aged 35 and 65 years. Fat percentage increased 36 per cent in women and 30 per cent in men between the groups aged 35 and 65 years. There was a difference in waist/hip ratio (WH ratio) between men and women at all age groups. Of the women 46 per cent had WH ratios above 0.8 and 14 per cent of the men had WH ratios above 1.0, suggesting that cut-off points for WH ratio as an indicator of cardiovascular risk are population specific. This may be caused by a different distribution of other cardiovascular risk factors in the Danish population than in other populations. Men had larger WH ratios per body fat mass with age, whereas in women there was no effect of age on this relation. Furthermore the WH ratio increments in this population took place before the age of 55 years in men, but after 55 years in women. The results may contribute to explain gender differences in morbidity and mortality with increasing age.