The late Eocene Chesapeake Bay impact structure is a well-preserved example of one of Earth's largest impact craters, and its continental-shelf setting and relatively shallow burial make it an excellent target for study. Since the discovery of the structure over a decade ago, test drilling by U.S. federal and state agencies has been limited to the structure's annular trough (Figure 1). In May 2004, the U.S. Geological Survey (USGS) drilled the first scientific test hole into the central crater of the Chesapeake Bay impact structure at the town of Cape Charles, Virginia (Figure 1). This partially cored test hole, the deepest to date, penetrated postimpact sediments and impact breccias to a total depth of 823 m. The test hole is located on the eastern flank of the crater's central uplift, as inferred from seismic surveys and potential-field maps. Two groundwater observation wells were installed within the single test hole with screens at depths of 415--421 m and 689--695 m. The bottom 79 m of the test hole and a short interval at 427--433 m depth were cored with moderate recovery. Drill cuttings were collected from the uncored intervals. A suite of geophysical logs was acquired for the full length of the hole. Rock types and pore-water salinities encountered in this new hole are significantly different from those sampled previously in the structure's annular trough.