Zinc and copper are common components of aquatic effluents from various industrial and mining sources. The acute toxicity of various compounds of Cu and Zn has been determined for many species of fish using continuous flow as well as static toxicity tests under different chemical, temperature, and temporal regimes. Similarly, the toxicity of mixtures of these two, as well as of more complex mixtures of heavy metals, has been studied by many researchers. While many of these studies report the toxicity of Cu and/or Zn to the bluegill (Lepomis macrochirus), to the authors knowledge the literature does not mention the acute toxicity of mixtures of these two metals to this species. The present study was undertaken to investigate the acute toxicity of divalent Zn-Cu mixtures to the bluegill.