BACKGROUND: The outbreak of severe acute respiratory syndrome (SARS) posed an unprecedented threat and a great challenge to health professionals in Hong Kong. The study reported here aimed at investigating the origin of stress and psychological morbidity among frontline healthcare workers in response to this catastrophe. METHOD: Self-administered questionnaires were sent to frontline healthcare workers in three hospitals. The General Health Questionnaire was used to identify psychological distress. Socio-demographic and stress variables were entered into a logistic regression analysis to find out the variables associated with psychological morbidity. RESULTS: The response rate was 40 %. Sixty-eight per cent of participants reported a high level of stress. About 57 % were found to have experienced psychological distress. The healthcare workers' psychological morbidity was best understood by the perceptions of personal vulnerability, stress and support in the workplace. CONCLUSION: These findings shed light on the need for hospital administrators to be aware of the extent and sources of stress and psychological distress among frontline healthcare workers during disease outbreak.