Limiting attention only to those cases where significant overburden lift cannot be achieved by use of explosives, i.e., to relatively deep oil shale seams, it was concluded that the two rubblization techniques which essentially constitute the current bed preparation technology, namely, the wellbore springing and hydraulic/explosives fracturing concepts, both have inherent traits which will prevent them from ever becoming useful for practical applications. Difficulties with the wellbore springing concept stem largely from the cylinderical geometry which leads to rapidly attenuating stress waves (hence to comparatively small fractured regions) and to the creation of a residually stressed region around the explosive cavity that restricts fluid flow and hinders void redistribution efforts. Major problems with the hydraulic/explosive fracturing concept are that many operations cannot be controlled and that regions of enhanced permeability are formed only in the vicinity of explosive-filled hydrofractures. The experimental, theoretical and phenomenological information used in the assessment that led to the above conclusions is discussed in detail in the report. The physical characteristics of a successful bed preparation concept are defined along with recommendations for a research-oriented program which would lead to the development of the technology necessary to achieve a successful true in situ retorting capability.