Background: It has recently been suggested that regular treatment with racemic β₂-adrenoceptor agonists might result in bronchial hyperresponsiveness (BHR) to a range of spasmogens, and this might be due to adverse effects of the distomer. Objective: We sought to determine whether BHR induced by means of continuous exposure to racemic and S-albuterol was mediated by sensory nerves. Methods: Naive or ovalbumin-sensitized guinea pigs were treated for 10 days with RS-, R-, or S-albuterol (1 mg·kg⁻¹·d⁻¹) through subcutaneously implanted minipumps. Lung function was then determined in response to a number of spasmogens and assessed on the basis of an increase in total airway resistance. A separate group of animals were chronically treated with capsaicin (80 mg/kg) before the albuterol treatment. Results: Treatment with RS- or S-albuterol increased airway responsiveness to bradykinin, leukotriene C₄, and capsaicin in naive guinea pigs (P < .05) and to histamine and ovalbumin in immunized guinea pigs (P < .05). Chronic treatment with capsaicin prevented the development of RS- and S-albuterol-induced BHR in these models. The bronchodilator efficacy of acute intravenously administered RS-albuterol was unaffected in RS-, R-, or S-albuterol-treated guinea pigs compared with in vehicle-treated animals. Conclusion: We have provided evidence demonstrating that continuous exposure to RS- and S-albuterol increases bronchial responsiveness to a range of stimuli, an effect not attributed to β-adrenoceptor occupancy or desensitization. Furthermore, capsaicin-sensitive sensory nerves mediate the development of BHR, at least in part. (J Allergy Clin Immunol 2002;110:388-94.)