Leukotriene modifiers are the first new class of drugs for the preventative treatment of asthma to be launched in the Western world for more than 20 years. In the US, there is now more than 1 year of clinical experience with this class of compounds, but just where exactly do these agents fit into clinical practice? This question was raised at the 1998 International Conference of the American Lung Association and the American Thoracic Society [Chicago, US;April 1998]. Asthma treatment guidelines recommend these agents as alternatives to low-dose inhaled corticosteroids in patients with mild persistent asthma. But are these the only patients who will benefit from treatment with these new orally active agents?