Injection of waste liquids into Florida's subsurface is physically feasible in many places but should be accompanied by monitoring of the waste‐receiving aquifer system in addition to the injection facility. Monitoring of the interaction of factors including hydrogeologic conditions, well construction, waste volumes and characteristics, and potable‐water sources is desirable to assure that fresh‐water resources are not being adversely affected. An effective aquifer‐system monitoring program includes on‐site wells located close to an injection well and open to the next‐higher permeable stratum, satellite wells located hundreds to several thousands of feet from an injection well and open to the receiving aquifer, and regional wells located miles from individual injection wells and open to the receiving aquifer. An extensive aquifer‐system monitoring program associated with two waste‐injection facilities near Pensacola, Florida, has provided data which have aided hydrologists to understand the aquifer system's response to the injection and, accordingly, to evaluate the potential for affecting the area's fresh‐water resources.