As a review, the hypothesis being tested in this program was that crushing to finer crush sizes liberates more high grade oil shale thereby allowing for increased oil recovery at higher grades. Heavy medium technology utilizing dynamic vessels can successfully upgrade properly sized oil shale. It should be stressed that the shale must be well screened to remove -28 mesh material to allow for successful plant operation. The fines if not removed an result in significant operating problems by increasing the viscosity of the medium being used. As a review, the medium mixes used for this study would suggest that, at necessary gravities of separation, a mixture between magnetite and ferrosilicon will be necessary in an operating plant. The pilot plant results suggest that some small advantage does exist in the grade recovery relationship as a function of top crush size. As the crust size decreases, a higher grade product can be recovered. For the 3/4''and 3/8''crust size, however, this product will not be better than 0.5 to 1.0 gallon per ton higher in grade as the crush size is decreased from 3/4''to 3/8''. Judging only on the heavy liquid results, here appears to be no great advantage to crushing beyond 3''for upgrading by heavy medium techniques. The true economic balance will be between final grade produced and the economics of retorting and handling of the tailings material. From the work presented herein it would appear as if no more than a two gallon per ton advantage will be achieved in the final product by crushing from say 1-1/2''to 3/8''. It is apparent that within the 28 mesh fraction, higher grade samples at internally higher recoveries can be achieved; however, when compared to the total oil feeding the plant, i.e., total ore, these recovery grade improvements are diminished. 11 figs., 16 tabs.