Scombroid fish poisoning is an acute illness that occurs after eating fish containing high levels of histamine or other biogenic amines. Symptoms typically include facial flushing, sweating, rash, a burning or peppery taste in the mouth, diarrhea, and abdominal cramps and usually resolve within several hours without medical intervention. More severe symptoms (e.g., respiratory distress, swelling of the tongue and throat, and blurred vision) can occur and require medical treatment with antihistamines. In late 2006, two outbreaks of scombroid fish poisoning occurred, one in Louisiana and one in Tennessee. To determine the source of the outbreaks and to implement control measures, CDC and the state health departments in Louisiana and Tennessee conducted epidemiologic investigations, and the Food and Drug Administration (FDA) conducted traceback investigations of the product. This report describes the results of those investigations, which indicated that the outbreaks in Louisiana and Tennessee were associated with tuna steaks from Indonesia and Vietnam, respectively. The majority of seafood eaten in the United States is imported. FDA programs to identify and prevent seafood hazards such as scombroid fish poisoning have made substantial progress but are able to inspect only a small proportion of seafood entering the United States. The only effective method for prevention of scombroid fish poisoning is consistent temperature control of fish at ≤40°F (≤4.4°C) at all times between catching and consumption.