Synergism and antagonism of cadmium (Cd), copper (Cu) and selenium (Se) to biological toxicities in red soil, yellow brown soil and black soil were evaluated by MICROTOX method. The relation between forms of the tested metals in soil and the synergism or antagonism between them was also studied.Results showed that owing to the difference of soil chemical properties, toxicity of these metals in soils was different. In red soil with acid reaction and low in cation exchange capacity, antagonism occurred significantly between metals when they coexisted at high concentrations, while synergism occurred only under low concentrations. It is indicated that in red soil, toxicity of metals affected by synergism or antagonism depends on concentration of the metals present. For yellow brown soil and black soil with larger cation exchange capacity and lower exchangeable aluminium (A1), no toxicity of metals was observed even if metals were added to soil in high concentrations. Synergism and antagonism between Cd, Cu Synergism and antagonism of cadmium (Cd), copper (Cu) and selenium (Se) to biological toxicities in red soil, yellow brown soil and black soil were evaluated by MICROTOX method. The relation between forms of the tested metals in soil and the synergism or antagonism between them was also studied. Results showed that due to the difference of soil chemical properties, toxicity of these metals in soils was different. In red soil with acid reaction and low in cation exchange capacity, antagonism occurred significantly between metals when they coexisted at high concentrations, while synergism occurred only under low concentrations. It is said that in red soil, toxicity of metals affected by synergism or antagonism depends on concentration of the metals present. For yellow brown soil and black soil with larger cation exchange capacity and lower exchangeable aluminum (A1), no toxicity of metals was observed even if metals were added to soil in high concentrations. Synergism and antagoni sm between Cd, Cu