BACKGROUND AND AIM: Although some metal exposures (Pb, Cd) have declined over time in the general US population, it is not known if American Indian (AI) communities experienced similar declines attributable to similar sources. Our objectives were to a) characterize trajectories of blood metal changes over time, and b) to identify characteristics of participants who experienced larger declines in blood metal concentrations in the Strong Heart Family Study (SHFS). METHODS: As, Cd, Pb, Mn, Hg, Ni, Se, and Zn were measured in whole blood samples from 310 SHFS participants at visit 3 (1997-1999) and visit 5 (2006-2009). We estimated the percent reduction in geometric mean of each metal across subgroups, used growth mixture models to identify trajectory classes of blood metal change, and evaluated the probability of trajectory class membership by subgroup via generalized estimating equations and logistic regression. RESULTS:Overall, percent geometric mean declines were 13% (As), 15% (Cd), 39% (Pb), 7% (Mn), 28% (Ni), 3% (Se), and 19% (Zn). Cd declines were largest for former smokers (26%), participants 30 years old (19%), and participants from North/South Dakota (30%). Pb declines were largest for participants from Arizona and Oklahoma (51%), former smokers (45%), and participants 30 years old (44%). The adjusted odds of being in the Cd High-Decreasing trajectory were higher for females vs. males (odds ratio 1.10, 95% CI 0.50, 2.40) and participants from North/South Dakota vs. Arizona (8.15, 95% CI 1.74, 38.0). The odds of being in the Pb High-Decreasing trajectory were lower for females vs. males (odds ratio 0.61, 95% CI 0.32, 1.16) and participants from Oklahoma vs. Arizona (0.57, 95% CI 0.22, 1.48). CONCLUSIONS:Substantial variability in the recent decline in blood metal concentrations exists across subgroups within the SHFS, indicating that declines in metal exposures in recent decades were not uniform across these AI communities. KEYWORDS: metals, American Indian, lead, arsenic, trends