The toxicity of some pesticides, namely, Lontrel, Sencor, Roundup, Bentazon, and Hymexazol, and also Lontrel complexes with Cu, Co, Mn, Mg, Mo, Ni, and Zn that are being widely used in agriculture and, hence, abundant in the environment were characterized by biotesting. The variation in the enzymatic activity of the luminous bacteriaBeneckea harveyi and in the reproductive function of the infusoria Tetrahymena pyriformis was measured and used to determine toxicity factors. The toxicity of the above compounds was found to correlate with their ability to form stable complexes with adenosine triphosphate (ATP).