The Bureau of Mines performed limited field studies during 1976-77 in 4.3 million acres of land within the Eastern Brooks Range to provide the additional mineral information requested by the Federal- State Land Use Planning Commission of Alaska. Because of size, remoteness of the area, time constraints, and restricted funding, the findings of this report are only preliminary. A reconnaissance was made through a major portion of the project area to more adequately define regions of mineral potential. A total of 964 stream sediments and 42 rock samples were analyzed. The study area is divided into four geologic terranes based on a review of the available literature.