Introduction: Field work during the 1952 field season has supplied new data on the areal extent, composition, and estimated reserves of uranium-bearing carbonaceous rocks in the Fall Creek.area, Bonneville County, Idaho. The following is a preliminary report of progress to describe these new data which supplement the information contained in Trace Elements Memorandum Report 340 (Vine and Moore, 1952). This work was done on behalf of the Division of Raw Materials of the U. S. Atomic Energy Commission.