Fourteen experimental ponds were dosed with the energy-related polynuclear aromatic hydrocarbon fluorene to effect nominal concentrations of 0.12, 0.5, 2.0, 5.0, and 10.0 mg/L. Measurement of emergent aquatic insects revealed no effects due to fluorene application. Zooplankton density was drastically reduced by treatments at 5.0 and 10.0 mg/L; however, it recovered in one to three weeks due to an increase in the number of rotifers that replaced the crustacean zooplankton killed by fluorene. Species richness of the zooplankton community was also reduced by the treatments at 5.0 and 10.0 mg/L. The survival and yield of both largemouth bass (Micropterus salmoides) and bluegills (Lepomis macrochirus) were reduced by the treatment at 0.12 mg/L, as were the production and survival of bluegill recruits. The mean increase in weight of adult and recruit bluegills was inversely related to the number surviving, indicating that fluorene toxicity induced a secondary response in the restructuring of the fish community. A comparison of algae and invertebrate laboratory toxicity test results with data from the pond studies revealed that these organisms were more sensitive to fluorene in the laboratory. However, the two species of fish in the ponds were more sensitive to fluorene than in routine laboratory tests.