Scombroid fish poisoning is a food-borne chemical intoxication caused by certain spoiled fish that contain a large amount of histamine and some biogenic diamines. It has gradually become a world-wide medical problem and probably is the most common cause of fish poisoning. As the data on the incidents of scombroid fish poisoning in Taiwan remains scarce, we report 2 incidents of scombroid fish poisoning in Northern Taiwan. We collected data of the 2 outbreaks of suspected fish poisoning which were reported to us in 1996. An epidemiological investigation was undertaken. Questionnaire interviews were given to persons who ate lunch in the same cafeteria in outbreak 2. The leftover fish were sent for species identification and toxin analysis. The first incident involving 4 women occurred in March 1996. All cases experienced flush, dizziness, blurred vision and skin rashes after eating lunch. A non-scombroid fish of Makaira with histamine levels as high as 84.13 mg/100 g flesh was implicated in this incident. In August 1996, another incident involving some cases who ate lunch at the same cafeteria were investigated. A total of 146 questionnaires were distributed with a return of 132 questionnaires (90.4%). Fifty-five employees reported positive signs or symptoms; 48 persons who ate fish and 7 women who did not eat fish were ill. Fish was the only food associated with the illness with an attack rate of 73.8% (p < 0.001). The incriminated fish was later identified as a scombroid fish of Euthynnus with a histamine content of 271.9 mg/100 g flesh in 1 leftover piece and 118.5 mg/100 g flesh in another piece. Most cases in these 2 outbreaks received treatment with antihistamines and had rapid and complete recovery. The diagnosis of scombroid fish poisoning could be misdiagnosed as food allergy or bacterial food poisoning if physicians are not aware of such poisoning. The nonspecific but characteristic symptomatology of histamine food poisoning and previous consumption of fish should alert physicians to the possibility of scombroid fish poisoning. Unless complicated with shock or respiratory distress, supportive treatment with antihistamines usually concludes with a good prognosis. Toxin analysis of the fish flesh remains the most important step in approaching a confirmed diagnosis.