This is one of a series of summary reports that present the findings of reconnaissance-type mineral assessments of certain lands in Alaska. The Utukok and Colville Rivers rise near the eastern end of the De Long Mountains in the southern part of the National Petroleum Reserve-Alaska (NPR-A). Historically, both have been important surface travel routes. NPR-A has been closed to mineral entry since the 1920's. The Utukok River heads in a little known part of a mineralized trend characterized by stratiform zinc-lead-silver deposits with barite and fluorite. Exposures of coal, mostly bituminous, are known along the Utukok River generally from Archimedes Ridge and Carbon Creek downstream to the mouth. The Colville River Valley is north of any recognized metallic mineral trends although most tributaries from the south head into mineralized areas. Dominantly bituminous coal occurrences are known from the mouth of the Etivluk River downstream to within 20 miles of umiat. Subbituminous coals have been reported at intervals from there to the beaufort sea. Both the Utukok and Colville Drainage Basins have rock environments similar to those in which sedimentary uranium deposits occur elsewhere, but this possibility remains unevaluated.