Includes Executive Summaries from a series of four STAC workshops held in 1990-1991 that deal with key contaminant issues as related to Chesapeake Bay system processes and living resources. The workshops addressed major categories of toxicological research, including suborganismal toxicity testing, whole organism toxicity, contaminant fate and transport, and ecological risk assessment. Also discussed are recommendations for ambient toxicity studies that resulted from an 1989 STAC workshop on Ambient Toxicity Assessment.