A series of basic analyses was performed to disclose the problems in the measurement of waist circumference (WC) at umbilical level, which will provide quite important parameters in the national annual health check for metabolic syndrome coming in April, 2008 in Japan.WC and body fat ratio was measured in 53 healthy volunteer, especially in 10 subjects (male 10, female 10), measurements were done by 5 examiners identically to disclose inter-examiner variances, changes due to respiration maximal depression of abdomen (or maximal intentional depression of WC), and eating and after lunch.WC tended to be higher in aged male, than aged and young female, and was positively correlated with body fat ratio. Minimal and maximal inter examiner variances of WC were 0.3 and 4.7cm, respectively. We need to pay attention to it. The effect of respiration and eating lunch were relatively low and may not cause serious problems. Intentional depression of abdomen caused from 2 to 8.1cm decrease of WC, which could provide false negative results.WC measurement seems to be easy but actually it is difficult. We need to remind some difficulties or preanalytical or analytical problems in this easy looking examination, especially used in large scale screening test.