Toxicological studies have shown that metals directly or indirectly influence testosterone (T) production, but the data from humans is limited and inconsistent. The aim of this study was to examine the associations between urinary metal concentrations and circulating Tin Chinese men. Urinary concentrations of 13 metals (arsenic, cadmium, cobalt, chromium, copper, iron, lead, manganese, molybdenum, mercury, nickel, selenium and zinc) and serum levels of T were analyzed in 118 men from an infertility clinic. Multivariable linear regression was used to assess the effect of metals exposure on T. Among the measured metals, the median urinary Zn (359.36 mu g/g creatinine) and Co (0.16 mu g/g creatinine) concentrations were the highest and the lowest, respectively. Significant dose-response relationships were found between decreased T and urinary Mn and Zn, even when considering multiple metals (both P for trend <0.05). Our results indicate that elevated Mn and Zn are inversely associated with T production. (C) 2013 Elsevier Inc. All rights reserved.