To investigate the practicality of hypothermia and hypometabolism as sensitive indices of toxicity in the mouse, oxygen consumption was monitored continuously and body temperature was measured at 30 min post-injection following the intraperitoneal administration of various metal salts. Eleven metal ions were tested: Al(3+), Cd(2+), Co(2+), Cr(2+), Cu(2+), Hg(2+), Mg(2+), Mn(2+), Ni(2+), Pb(2+), and Zn(2+). All metals induced dose-dependent reductions in both oxygen consumption (hypometabolism) and deep body (colonic) temperature. Comparative toxicity of the metal ions was evaluated by calculating the dose of metal ion in dimensions of mmole/kg body mass needed to reduce colonic temperature to 35C. The order of toxicity from lowest to highest was as follows: Cr