We investigated the effect of inhalation of cotton bract extract (CBE) on bronchial responsiveness to methacholine. Six (6) healthy volunteers were exposed to CBE or SHAM (normal saline) in a double-blind, random, cross-over fashion with measurements of non-specific bronchial responsiveness prior to and 10 minutes following provocation. For the group, no hyperresponsiveness developed (P > 0.05) in the period immediately following CBE challenge.