To evaluate cytochrome P-450 related parameters as biomarkers of pollutant exposure, rates of arylhydrocarbon hydroxylase (AHH), ethoxyresorufin-O-deethylase (EROD), benzyloxyROD (BROD), pentoxyROD (PROD) and ethoxycoumarinOD (ECOD) were studied in 10-day-old BCNHs (Nycticorax nycticorax). Nestlings were collected from Chincoteague National Wildlife Refuge, VA ('controls') and from polluted sites including. Cat Island, Green Bay, WI, and Bair and West Marin Islands, San Francisco Bay, CA. Livers were frozen (-70.C) for monooxygenase assays and SDS-PAGE. Microsomal AHH and BROD activities were greater (P2 standard deviations from the control mean (induced up to 3-fold). EROD, PROD and ECOD did not differ among sites. Absence of an EROD response with AHH and BROD induction in BCNHs is different than responses in other species. The association of pollutant burdens with P-450 parameters is being studied. These biomarkers may serve as a rapid screen of exposure in a national contaminant biomonitoring program and other assessment activities.