The authors describe an outbreak of beriberi in a detention center in Taiwan and examine risk factors for illness. A survey was conducted among a sample of 176 randomly selected detainees. A menu-assisted dietary recall method was used to obtain diet information from nine hospitalized detainees. A probable case patient was defined as an individual who had at least two of the following characteristics: leg edema, weakness of the extremities, poor appetite, and dyspnea. Possible case patients were those who had only one of these characteristics. Of the 176 survey respondents, 19% were classified as probable case patients and 40% as possible case patients. The mortality rate based on probable cases was 1.1%. Body Mass Index (BMI) was negatively associated with illness (p < 0.0001), and length of stay in the detention center was independently positively associated with illness (p < 0.05). The average intake of dietary thiamine among the nine hospitalized case patients who completed three-day dietary recall surveys was 0.49 +/- 0.1 mg/day. After thiamine administration, all symptoms and signs of beriberi resolved. This outbreak is a reminder of the importance of ensuring adequate diets for poor, institutionalized, or refugee populations who are unable to supplement their diets.