Laboratory experiments were carried out to evaluate the effectiveness of antibacterial substances and antibiotics against Thiobacillus ferrooxidans, the organisms responsible for bacterial mediated acidic mine drainage. Twenty two antibiotics (obtained from Lilly and Co.) and two antibacterial substances were added to: bacterial culture ATCC 19859 grown in 9K medium. Appropriate controls were maintained. Inhibition of iron oxidizing bacteria was recorded in terms of changes in Eh of the medium treated with the compound. Seven antibiotics (A38533A:, A38533B, 197506, 13780, 171541, chloramphenicol and cephalexin) and the two antibacterial substances [N-serve(nitrapyrin) and Dicyandiamide] effectively inhibited the oxidation of Fe²⁻ ions in the medium. The kinetics of Fe²⁻ oxidation with the addition of antibiotics and the antibacterial substances was studied. N-serve [2-chloro-6-(trichloromethyl) pyridine], used as a nitrification inhibitor in agriculture, was highly effective at concentrations greater than 0.1 ml/l. Iron oxidation levels were reduced to levels close to that in uninoculated controls (abiotic oxidation). The use of N-serve to inhibit acid mine drainage (AMD) causing bacteria seems to be both economical and environmentally safe. / Master of Science