Blood samples and 24-h duplicates of food were collected in the years around 1980 and then in 1990's from inhabitants of nonpolluted regions in Japan. The 1990 study is still in progress with 286 blood samples and 125 food duplicates already collected from 7 regions. A preliminary analysis is made in the present study with the data obtained from the 7 study regions where the survey was conducted in 1980 and then in 1990, to examine possible changes in dietary cadmium intake (Cd-D) and consequently cadmium levels in blood (Cd-B) during this 10 year period. The food duplicate analysis showed that Cd-D in 1980 was 47.1 micrograms/day (1.74):65 [GM (GSD):N] for men and 27.7 micrograms/day (1.75):65 for women. The counterpart values in 1990 were 29.5 micrograms/day (1.66):40 for men and 23.8 micrograms/day (1.73):85 for women; the difference between the two values for the same sex is significant (P < 0.05) both in men and in women, suggesting that there occurred about 37% and 14% reduction in dietary cadmium intake during this 10 year period in men and in women, respectively. Comparison in Cd-B showed that Cd-B for men and women in 1990 were 1.79 micrograms/l (2.01):121 and 1.84 micrograms/l (1.67):165, respectively, whereas the counterpart values in 1980 were 3.84 micrograms/l (1.64):123 and 3.57 micrograms/l (1.42):141, respectively, indicating significant (P < 0.01) reduction in Cd-B in both sexes in parallel to the reduction in Cd-D.(ABSTRACT TRUNCATED AT 250 WORDS)