This study addressed habitat availability and use by endangered pallid sturgeon (Scaphirhynchus albus) in the Fort Randall segment of the Missouri River. Physical aquatic habitat - depth, velocity, and substrate - was mapped in 15 sites in Augsust and October of 2002. Habitat assessments were compared with fish locations using radio telemetry. Results indicate that pallid sturgeon preferentially use locations in the Fort Randall segment deeper than the average available habitat, with prominent usage peaks aat 3.5-4.0 m and 6-6.5 m, compared to the modal availability at 3-3.5 m. The fish use habitats with a modal velocity of 80 cm/s; the used velocities appear to be in proportion to their availability. Fish located preferentially over sand substrate and seemed to avoid mud and submerged vegetation.