Industrial wastewater from two synthetic-fiber manufacturing plants has been injected into the Lower Floridan aquifer near Pensacola, Florida, since 1963, and near Milton, Florida, since 1975. Trend analysis of selected water-quality characteristics in water from four monitoring wells at each of these plants indicates that injected wastewater has affected ground-water quality in the Lower Floridan aquifer, which contains nonpotable water, up to 1.5 miles from the injection wells at the plant near Pensacola and at least 0.3 mile from the injection wells at the plant near Milton. No evidence for upward seepage of injected wastewater through the overlying Bucatunna Clay to the Upper Floridan aquifer was found at either of the plants.