The toxicity of sediments in Biscayne Bay and many adjoining tributaries was determined as part of a bioeffects assessments program managed by NOAA's National Status and Trends Program. Biscayne Bay was selected by NOAA for this survey because data from the NS&T Mussel Watch Program and data from previous surveys of the bay had shown a potential for toxicity and other adverse biological effects. In addition, no bay-wide information had been generated on the toxicological condition of the bay sediments and several agencies had indicated a need for this type of data and a willingness to assist NOAA in collecting them. The study area was defined as extending from Dumbfoundling Bay at the north end to Little Card Sound at the south end, seaward to the barrier islands or reef, and landward to the shoreline or saltwater control structures. This area was determined to encompass a total of 484 kilometers of the sea floor. During 1995 and 1996, 226 samples were collected from randomly-chosen locations and tested for toxicity and analyzed for chemical concentrations. Data from these tests and analyses are included in the report. Samples for benthic community analyses were collected at one-third of the stations; however, data from those analyses are not included in the report but are available from NOAA's online database http://nbi.noaa.gov/mapBiscaynebay.aspx.The survey was designed to characterize sediment quality throughout the greater Biscayne Bay area. Surficial sediment samples were collected during 1995 and 1996 from 226 randomly-chosen locations throughout nine major regions. Laboratory toxicity tests were performed as indicators of potential ecotoxicological effects in sediments. A battery of tests was performed to generate information from different phases (components) of the sediments. Tests were selected to represent a range in toxicological endpoints from acute to chronic sublethal responses. Toxicological tests were conducted to measure: reduced survival of adult amphipods exposed to solid-phase sediments; impaired fertilization success and abnormal morphological development in gametes and embryos, respectively, of sea urchins exposed to pore waters; reduced metabolic activity of a marine bioluminescent bacteria exposed to organic solvent extracts; induction of a cytochrome P-450 reporter gene system in exposures to solvent extracts; and reduced reproductive success in marine copepods exposed to solid-phase sediments.The full report is available online at http://www8.nos.noaa.gov/cit/nsandt/download/documents/BI1/BI1_report.pdf