Typically, a wide variety of chemicals are found concurrently in the environment, which makes identifying the contribution of individual toxicants difficult. For the purposes of this study, the toxicity of paired metals to the nematode Caenorhabditis elegans was investigated. Toxicity tests were designed to first determine LC50 values for single metal exposure and then the tests were rerun with a second metal present to observe the effect on the previous LC50 values. Four-day-old adult nematodes were exposed to paired combinations of Cd, Zn, Pb and Hg for 24 h without food. Exposures with paired metals showed a variety of interactions which ranged from antagonistic to synergistic effects.