Objective: To examine relationships between the ratio of energy intake to basal metabolic rate (EI/BMR) and age and body mass index (BMI) among Japanese adults. Design: Energy intake was assessed by 4-day semi-weighed diet records in each of four seasons (16 days in total). The EI/BMR ratio was calculated from reported energy intake and estimated basal metabolic rate as an indicator of reporting accuracy. Setting: Residents in three areas in Japan, namely Osaka (urban), Nagano (rural inland) and Tottori (rural coastal). Subjects: One hundred and eighty-three healthy Japanese men and women aged $ 30 years. Results: The oldest age group ($ 60 years) had higher EI/BMR values than the youngest age group (30 -39 years) in both sexes (1.74 vs. 1.37 for men; 1.65 vs. 1.43 for women). In multiple regression analyses, age correlated positively (partial correlation coefficient, b ¼ 0.012, P , 0.001 for men; b ¼ 0.011, P , 0.001 for women) and BMI correlated negatively (b ¼ 2 0.031, P , 0.001 for men; b ¼ 2 0.025, P , 0.01 for women) with EI/BMR. Conclusion: Age and BMI may influence the relative accuracy of energy intake among Japanese adults. . In particular, underreporting of energy intake is a serious threat to the validity of self-reported dietary assessment data. Studies using the doubly labelled water technique as an external biomarker of energy intake not only reveal underreporting of energy intake, but also identify the subject characteristics and factors associated with underreporting 3,4 . Moreover, other studies using the ratio of energy intake to basal metabolic rate (EI/BMR) as an alternative approach to identify the low energy reporters have shown similar results 5,6 . Most studies found a higher proportion of underreporting among women and older subjects 7,8 . Moreover, underreporting of energy intake was common among obese subjects 9 -11 , but was also observed in non-obese subjects 12,13 . Other factors such as body image, health consciousness, social desirability, educational level and smoking status also affected reporting accuracy 2,14,15 . However, all of these studies were conducted in Western countries. The only study conducted in Japan showed a significantly negative correlation between BMI and EI/ BMR among women aged 18 -20 years 16 . Thus the purpose of the present study was to examine the relative accuracy of self-reported energy intake among various age ranges in the Japanese population.