Extracts purified from cotton bracts are known to cause bronchoconstriction in humans and monkeys. Although these same partially purified extracts cause contraction of various animal smooth muscle preparations in vitro, airway inflammation is thought also to be an important determinant of the bronchoconstriction and bronchial hyperreactivity observed in humans following inhalation challenge with these extracts. At the cellular level, the bract extracts have been shown to activate bronchoalveolar lavage cells to release inflammatory mediators which include chemotaxin(s), superoxide, and thromboxane. All of these biological activities are caused by purified extracts which we showed previously contain a highly water soluble components of less than 1,000 molecular weight. Further fractionation of the bract extract has yielded four sub-fractions, each consisting predominately of one of the four major components in the bract extract and each exhibiting characteristic UV and fluorescence spectra. Fast atom bombardment mass spectrometry of the sub-fractions detected the presence of small molecular weight species exclusively, with species above 500 daltons being found only in one subfraction.