STUDY OBJECTIVE: To determine whether rapid-incremental work rate (IWR) testing would be as useful as standard high-intensity constant work rate (CWR) protocols in eliciting exercise-induced bronchoconstriction (EIB) in susceptible subjects. DESIGN AND SETTING: A cross-sectional study performed in a clinical laboratory of a tertiary, university-based center. SUBJECTS AND MEASUREMENTS: Fifty-eight subjects (32 males, age range, 9 to 45 years) with suspected EIB were submitted to CWR testing (American Thoracic Society/European Respiratory Society guidelines) and IWR testing on different days; 21 subjects repeated both tests within 4 weeks. Spirometric measurements were obtained 5, 10, 15, and 20 min after exercise; a FEV1 decline > 10% defined EIB. RESULTS: Twenty-seven subjects presented with EIB either after CWR or IWR testing; 21 subjects had EIB in response to both protocols (kappa = 0.78, excellent agreement; p < 0.001). Of the six subjects in whom discordant results were found, two had EIB only after IWR. Assuming CWR as the criterion test, IWR combined high positive and negative predictive values for EIB detection (91.3% and 88.6%, respectively). Tests reproducibility in eliciting EIB were similar (kappa = 0.80 and 0.72 for CWR and IWR, respectively; p < 0.001). Total and intense (minute ventilation > 40% of maximum voluntary ventilation) ventilatory stresses did not differ between EIB-positive and EIB-negative subjects, independent of the test format. There were no significant between-test differences on FEV(1) decline in EIB-positive subjects (25.7 +/- 10.8% vs 23.7 +/- 10.0%, respectively; p > 0.05). Therefore, no correlation was found between exercise ventilatory response and the magnitude of EIB after either test (p > 0.05). CONCLUSIONS: Rapid-incremental protocols (8 to 12 min in duration) can be as useful as high-intensity CWR tests in diagnosing EIB in susceptible subjects. Postexercise spirometry should be performed after incremental cardiopulmonary exercise testing when EIB is clinically suspected.