Asthma is the most common chronic medical condition that school teachers may encounter among their pupils. However management of asthma in schools and the role school teachers adopt in this condition has only recently been explored. The aim of this study was to determine teachers' knowledge of asthma and its management. A postal questionnaire was circulated to 199 school teachers from 46 schools in Dublin City. A 74 per cent response rate was obtained. The number of children with asthma as identified by teachers was 7.8 per cent which suggests that asthma may be unrecognised in a number of pupils. Knowledge on signs and symptoms of asthma, provoking factors of asthma and the nature of the disease was generally satisfactory. However, knowledge on asthma medications, the purpose of inhalers and teachers' understanding of the treatment and management of asthma was considered poor. Knowledge on exercise-induced asthma was limited. There is a need to provide school teachers with education on asthma and its management. School policies on asthma also need to be developed with particular reference to action necessary in the event of an acute severe attack of asthma.