Abstract: Methods of treating a previously fractured bacteria contaminated subterranean formation penetrated by a well bore whereby the bacteria contamination is substantially reduced or eliminated are provided. The methods basically comprise mixing a bactericide with a fracturing fluid in an amount effective to contact and kill bacteria contained in the formation and pumping the mixture into the formation at a rate and pressure sufficient to re-fracture the formation. The re-fracturing of the formation causes the bactericide to be distributed throughout the formation and to contact and kill bacteria contained therein without adversely effecting the productivity of the formation.