The decrease in mercury (Hg) levels in whole blood (B), plasma (P), erythrocytes (Ery), and urine (U) was investigated in nine men after 3 d of intense (greater than 100 micrograms/m3) exposure to metallic Hg vapor. In a model in which common half-times for all subjects were used, the best fit for B-Hg was obtained with half-times of 3.1 d for a fast phase and 18 d for a slow phase. P-Hg seemed to decay more rapidly than Ery-Hg. Peak U-Hg (morning, creatinine-corrected samples) was not observed until 2-3 wk after exposure. Thereafter, the median half-time was 40 d (assuming individual one-compartment models). In a model for which common half-times were used, the point estimates were 59 d for a one-compartment model and 28 and 141 d for a two-compartment model. The fractions of the fast phases (i.e., two-compartment models with common half-times) were 80% for B-Hg and 84% for U-Hg.