Seismic reflection studies were performed across actively developing sinkholes located astride Interstate Highway 70 in Russell County, Kansas. Results indicate that high-resolution seismic reflection surveys are useful in the subsurface investigation of some sinkholes. In particular, we were able to delineate the subsurface vertical and horizontal extent of the sinkholes because of the excellent acoustical marker-bed characteristics of the Stone Corral anhydrite. The seismic reflection evidence presented here, combined with borehole information from 1967, suggest that the Stone Corral anhydrite has been down-dropped within one of the sinkholes as much as 30 m in 13 years. The seismic reflection method is potentially useful in engineering studies of other sinkholes and karst features. The seismic data presented here were obtained in the presence of relatively heavy highway traffic (i.e., up to a few dozen vehicles per minute) using the MiniSOSIE recording technique.