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Objective: This study aimed to analyse the influence of moderate changes in air temperature and humidity on the acute ventilatory response to exercise in asthmatic children. Design: 7 asthmatics over 15 years old (Experimental Group, EG), and 7 healthy subjects with the same characteristics (Control Group, CG) performed an exercise protocol in 2 different environments, interspaced by 48 hours: hot+humid environment (HH, temperature: 32.6±0.4°C, relative humidity: 42.4±1.6%) and an environment with less humidity+lower temperature (LHLT, temperature: 24.0±0.9°C, relative humidity: 36.3±1.3%). Steady state values of cardiorespiratory parameters were monitored during exercise, being the forced expiratory volume in 1st second (FEV1) and peak expiratory flow (PEF) obtained immediately before exercise and after 5 minutes of recovery. Results: The EG experienced a post-exercise decrease of FEV1 in LHLT (90.6±9.6%, p<0.05) and HH (95.2±5.8%, p<0.05) while CG did not show post-exercise changes in both environments (103.7±11.2% vs. 101.2±4.9%, respectively). The EG showed a post-exercise PEF decrease in the LTLH (94.6±8.8%, p<0.05) and no changes in the HH environment (99.7±4.2%), while CG did not show significant changes in both environments (102.9±12.7% vs. 107.0±9.8%). Conclusion: Results allow concluding that ventilatory response to exercise is influenced by air temperature and humidity, with a HH environment being more favourable for asthmatics. [ABSTRACT FROM AUTHOR]