Ground water is a valuable resource often used for industry, commerce, agriculture, and drinking water. In the 19080's, ground water provided 35 percent of the municipal water supplies in the United States and 95 percent of the rural, domestic drinking water. Scientists participating in ground-water studies may determine the potential pathways that contaminants could be transported in aquifers. In karst terrain especially, a contanimant can enter a fracture network in a carbonate aquifer and quickly spread to become a widespread health problem. Although Federal and local funding for ground-water cleanups and treatment may be available, the costs can exceed many millions of dollars each year. Such costly remedial actions could be avoided or minimized by becoming aware that ground water anywhere is vulnerable to contamination, but particularly so in carbonate terrain. Practicing good "out-of-doors" house- keeping is necessary. From the standpoint of economic and environmental responsibility, it is critical that we all work together to protect the quality of ground-water resources so that future generations can continue to have clean water.