Quantitative correlation among the four metals cadmium, copper, manganese, and zinc was examined in nearly 1500 urine samples collected from adult female inhabitants in 8 nonpolluted regions in various parts of Japan. In addition to a significant correlation between urinary cadmium and zinc as previously reported, copper levels significantly correlated with those of cadmium and zinc. In contrast, manganese did not show any significant correlation with cadmium, copper, or zinc. These findings are in agreement with the fact that cadmium, copper, and zinc are known to combine with metallothionein in vivo, whereas this is not the case with manganese.