Bluegill (Lepomis macrochirus Rafinesque) eggs, fry, juveniles, and adults were exposed to H2S concentrations to determine acute toxicity. Seventy-two-hour LC50 for eggs was 0.0190 mg/liter; 96-h LC50 for 35-day-old fry was 0.0131 mg/liter, for juveniles 0.0478 mg/liter, and for adults 0.0448 mg/liter. Exposure to lower levels of H2S resulted in some acclimation. Chronic exposure to sublethal levels of H2S for up to 826 days resulted in no egg deposition at 0.0022 mg/liter and reduced deposition after 97 days at 0.0010 mg/liter. Growth was adversely affected at levels from 0.0031 to 0.0107 mg/liter H2S depending on the life history stage at which chronic exposure was started. When exposure was started with eggs, the lower level retarded growth. Food consumption was reduced at 0.0085 mg/liter H2S. Time to anesthesia with MS:222 was reduced at levels from 0.0014 to 0.0031 mg/liter H2S. The most sensitive stage to acute toxicity was the feeding fry and to chronic toxicity was the spawning adult.