PURPOSE: to identify the symptoms of changes in the exhalation of asthmatic children. METHOD: this study was conducted with 30 children from 6 to 10 year-old, of both genders and with asthma clinical diagnosis confirmed by medical records and 30 non-asthmatic children from 6 to 10 year-old, of both genders, and with same age. We evaluated the nasal ventilation with Altmann millimeter nasal mirror measuring the nasal air escape in order to check their unilateral or bilateral air output and the relation of symmetry between the right and left nostril. The images were imported into the computer through HP scanner - Scanjet 2400 series. The analysis was performed by the Scion Image software for Windows (Alpha 4.0.3.2). All conclusions were based on a significance level of 5%, using Excel 2000 and SPSS v8.0 for the analysis. RESULTS: there were no significant differences between asthmatic and non-asthmatic children about the measurements of total area and the right and left nostril areas. CONCLUSION: there were no symptoms of changes in the exhalation of asthmatic children, being necessary a more specific study as for the nasal and pulmonary functions.