Extracts of DB 1/88 cotton dust contained oxidized (FMoxLP) and reduced FMLP, a chemoattractant peptide, and contracted guinea-pig isolated tractiealis (CPT) and aortic (CPA) smooth muscles. FMLP contracted CPT and GPA with EC50's of 91 and 14 nM, respectively. Human neutrophils induced large contractions of CPT. These findings suggest that FMLP associated with inhaled cotton dust could induce contraction of pulmonary vascular and airway smooth muscle by a direct action, and secondarily via recruited inflammatory cells.