This dissertation refers to the development of an in situ system devised to remediate soils contaminated with organic compounds. The system consists basically of a thermal probe capable of heating the soil matrix through radial flow and a thermal oxidizer that treats the resulting gases emissions. The system clearly reached the design aims. The thermal probe consistently programed temperatures up to 6000C to the soil matrix following applied thermal paths. The thermal oxidizer was capable to heat gases emissions up to 9000C under prolonged exposure. The experimental program was carried out using a residual soil from gnaiss taken from a slope at Washington Luiz Roadway. This soil was contaminated with used oil and submitted to a series of tests in order to assess the efficiency of the system developed herein. The results suggest that thermal desorption was able to reduce the degree of contamination to levels well below the limits established by National and International Environmental Agencies. The results also revealed the importance of aeration during the process to avoid the formation of coke. Fingerprinting tests carried out on gases emissions revealed that they were composed mainly by olefins and paraffins. The design of an in situ system as well as the termination criteria for in situ thermal desorption treatment might well be accomplished using the heat propagation theory developed by Stegemeier (1998).