The most feasible bioremediation technologies of unsaturated soils contaminated by Petroleum are (1) the on-site controlled remediation of the excavated contaminated plume in the contained system; and (2) the in situ sub-surface, highly controlled process in which nutrients and microbes or air are injected into the plume volume via a grid of wells and reversing the direction of the pumping. The detailed results of ex situ (controlled aerobic bioremediation) of ten sites with differing petroleum contamination and four in situ cases are reported and compared. It is concluded, that bioremediation of petroleum contaminated soil is an effective, safe and economically feasible remediation technique for the remediation of such contaminated sites, contingent on the providing of the site-specific appropriate conditions. However, the biodegradation rate of the NAPL is more variable in the in situ than in the ex situ aerobic process, correlating best in the latter with the molecular weight of the petroleum contaminants.