This chapter discusses basic microbial processes occurring during bioremediation and kinetics of bioremediation. It identifies optimum conditions for bioremediation and provides a discussion on a systematic approach for using bioremediation. Bioremediation processes can be used to treat contaminants present in the liquid phase, vapor phase and/or solid phase. Bioremediation processes can be classified into three main types: above-ground treatment of contaminated soils, above-ground treatment of contaminated water, and in situ treatment. In situ biodegradation can be enhanced through its combination with other technologies appropriate to the characteristics of the site and the contaminant. Accessibility of the site can be important in determining feasibility of bioremediation. Typical site conditions that are important are location of contaminant, availability of land, building or utility locations, and local population. Location of contaminant is important in determining whether nutrients, TEA, microbes etc. can be applied to the contaminated portion of the site.