Cross-bedded oolitic grainstones in the Ste. Genevieve Limestone (Mississippian) of the Illinois basin have generally been considered to be shallow marine. However, fine- to medium-grained cross-bedded grainstones of mixed clast type in the Ste. Genevieve of Harrison County, southern Indiana, are here interpreted to be of eolian dune origin on the basis of small-scale sedimentary structures, particularly climbing-wind-ripple structures. In addition, subaerial exposure of surfaces at the tops and bases of the eolian units is indicated by pedogenic features such as in-situ breccias and rhizoliths. Associated skeletal and oolitic grainstones of marine origin are distinguished from the eolian grainstones by the presence of pebble-sized fossils. The presence of several intervals of eolian deposits in the Ste. Genevieve is probably a result of eustatic sea level fluctuations.