"In situ or in place retorting has many potential advantages over the more conventional mining/ retorting approach. One of the major advantages is that in situ retorting avoids the costly and disfiguring mining and spent-shale disposal steps associated with the mining/retorting approach. Another potential advantage is that it may make it possible to recover oil from formations that are not amenable to the mining/retorting approach. Many investigators have recounted at length the problems of in situ retorting and Burwell, Sterner, and Carpenter have adequately referenced these investigations. Whereas it is not the purpose of this paper to delve into extended discussion of in situ retorting, it may help the reader to have on idea of the conditions under which in situ oils are produced. This paper will, therefore, describe briefly on situ experiment and a brief description will also be made of each of the retorts that produced the oil, with which the in situ oils will be compared. This paper will describe two crude shale oils that were recovered from successful in situ-combustion retorting experiments. The description will be based primarily on the results of the application of the Bureau of Mines crude shale-oil analysis to these two crudes. In addition to describing the properties of the two in situ crudes in terms of this analysis, the properties of crude shale oils from aboveground retorts will also be described. Comparison of the oils from the aboveground retorts with each other will be mode in order to determine the effect of change of retorting parameters upon oil character. Comparison of the in situ oils with the aboveground retort oil Is will allow explanation of the retorting conditions under which the in situ oils were produced. This indirect approach to the problem of describing the conditions under which in situ retorting is accomplished is necessary because of the inaccessibility of the retort zone to visual inspection, either during or after retorting."