[en] A hydrogeochemical and stream sediment reconnaissance for uranium in the Craig NTMS Quadrangle, Colorado, was conducted as part of the National Uranium Resource Evaluation. Totals of 1234 water and 1732 sediment samples were collected from 1743 locations over a 18,900 km² area at an average density of one location per 11 km². Water and/or sediment samples were collected from streams and springs. All water samples were analyzed for uranium and 12 other elements. Sediment samples were analyzed for uranium, thorium, and 41 additional elements. The uranium concentrations in water samples range from below 0.02 ppB to 856.44 ppB. The recalculated mean uranium concentration for all water types is 1.55 ppB. The recalculated mean was obtained after dropping five samples with values greater than 50.00 ppB. Waters with anomalous uranium concentrations were found in tributaries of streams that drain upper Cretaceous formations southwest of Craig, north of the Williams Fork Mountains, in Middle Park, and in an area underlain by Tertiary volcanics in the southeast corner of the Craig Quadrangle. Sediment samples from the quadrangle were found to have uranium concentrations that range from 1.53 ppM to 385.60 ppM, with a recalculated mean uranium concentration for all sediments of 6.23 ppM. The recalculated mean was obtained after dropping 13 samples with values greater than 50.00 ppM. Eight areas containing clusters of sediments with anomalous uranium concentrations are delineated. The two areas containing sediment samples with the highest uranium concentrations are in the Sand Wash basin and in the Park Range northeast of Steamboat Springs. Thorium concentrations in sediment samples range from 1.10 ppM to 1596.00 ppM with a mean of 26.75 ppM. Seven areas contain clusters of samples with individual thorium concentrations greater than 70 ppM. The areas containing the highest thorium values coincide with clusters of high uranium sediment samples in the Sand Wash basin