Two epidemiological studies aimed at investigating the dose-response relationship of environmental cadmium exposure were performed in a population living in the Kakehashi River basin, a cadmium-polluted area in Japan. In the first, the average cadmium concentration in rice from each village was used as an indicator of exposure and metallothioneinuria or beta 2-microglobulinuria as an index of renal tubular dysfunction. Dose-related increases in both the latter indices were observed. The total cadmium intake resulting in both metallothioneinuria and beta 2-microglobulinuria was calculated to be approximately 2 g for both sexes. In the second study, the dose-response relationship between urinary cadmium and metallothioneinuria or beta 2-microglobulinuria was evaluated in the same population. Prevalence rates increased proportionally with increasing urinary cadmium (Cd-U). The values of Cd-U corresponding to the prevalence rates of metallothioneinuria in the non-exposed population were calculated to be 4.2 micrograms/g creatinine for men and 4.8 micrograms/g creatinine for women; for beta 2-microglobulinuria the corresponding figures were 3.8 micrograms/g creatinine for men and 4.1 micrograms/g creatinine for women.