Blood cadmium (B-Cd) and seminal fluid cadmium (Sf-Cd) were measured in 120 adult male subjects not occupationally exposed to cadmium (Cd), comprising 42 nonsmokers (including nine former smokers) and 78 smokers. The respective median and range values were: 0.46 (0.19-1.49) microgram/l of B-Cd and 0.54 (0.17-1.67) microgram/l of Sf-Cd in nonsmokers, and 4.33 (0.49-13.33) micrograms/l of B-Cd and 0.85 (0.29-3.56) microgram/l of Sf-Cd in smokers. Both indicators showed a highly significant difference in Cd exposure between the groups (P < 0.0001), although the increase in B-Cd was considerably more pronounced than that of Sf-Cd in smokers compared with nonsmokers. The results suggest a nonlinear relationship (log Sf-Cd/log B-Cd: r = 0.501, P < 0.0001), rather than linear relationship (Sf-Cd/B-Cd: r = 0.430, P < 0.0001), between the indicators. Significant correlations were found between smoking habits, i.e., the number of cigarettes per day, and an increase in B-Cd in smokers (r = 0.296, P < 0.01) and in all 120 subjects (r = 0.685, P < 0.0001), as well as between smoking habits and an increase in Sf-Cd in smokers (r = 0.378, P < 0.001) and in all 120 subjects (r = 0.488, P < 0.0001). Both indicators are necessary for evaluation of individual internal Cd dose, since they appear to differ in reflecting recent and long-term cumulative Cd exposure and/or the amount of Cd at the site(s) of its effect(s) in the body.