Chemical spills that reach an aquifer in karst terranes do not behave like those in granular or highly fractured aquifers. Spills reaching diffuse-flow aquifers display relatively slow transport, are radially dispersive, and can be tracked through the use of monitoring wells. Spills in most karst terranes, however, are stored and transported in both the vadose and phreatic zones and do not exhibit radial dispersion. Actual contaminant transport in the phreatic zone of a karst aquifer may be extremely rapid to and highly concentrated at eventual discharge points, but the pollutant(s) cannot be tracked by any methods currently known. Contaminant attenuation is greatly limited in karst terranes. The unusual storage and transport characteristics responsible for the rapid transport and poor attenuation of contaminants in karst aquifers are a consequence of the unique properties of their flow system. Sinkhole development, the absence of surface water drainage, solutional enlargement of vertical fractures in the unsaturated zone, and the development of subsurface conduits (caves) are some of the properties of karst terranes that have substantial effects on the storage and transport of chemical contaminants.