Abstract: A method for reducing concentrations of hydrogen sulfide present in subterranean well fluids by injection of a stabilized solution of chlorine dioxide. The stabilized chlorine dioxide solution is introduced into the subterranean well by injecting the solution through the well bore. This method also includes the reduction of the hydrogen sulfide content in drilling mud which has been contaminated by hydrogen sulfide present in a hydrocarbon well by mixing a stabilized solution of chlorine dioxide with the drilling mud. This method requires the preparation of a stabilized chlorine dioxide solution, a determination of the approximate amount of hydrogen sulfide which might be brought to the surface by the drilling mud and the introduction of the predetermined amount of stabilized chlorine dioxide solution into the drilling mud.