A mass mortality of bottlenose dolphins (Tursiops truncatus) occurred along the central and south Atlantic coasts of the United States. Chemical residue analyses were performed on tissues from 1) a subset of dolphins that died during this event, 2) bottlenose dolphins that died after the mass mortality, 3) common (Delphinus delphis), and 4) white-sided (Laqenorhynchus acutus) dolphins taken incidentally in fishing operations. Average contaminant concentrations in adult males were higher than adult females. Females could be divided into two groups by contaminant concentrations, one with low concentrations and one with concentrations 4.4 times (PCBs) to 8.9 (p,p'-DDE) greater. Contaminant concentrations were generally greater than concentrations measured in either the common or white-sided dolphin. A subset of animals screened for unusual chemical contaminants showed numerous poly-brominated chemicals were present, including polybrominated bi-phenyls and diphenyl ethers not previously found in marine mammals from U.S. coastal waters.