Negative expiratory pressure (NEP) applied at the mouth during tidal expiration provides a non-invasive method for detecting expiratory flow limitation. Forty-two children were studied, i.e. 25 children with different respiratory symptoms (R) and 17 without any respiratory symptoms (NR). Children were examined without any sedation. A preset NEP of -5 cm H 2 O was applied; its duration did not exceed duration of tidal expiration. A significance of FL was judged by determining of a flow-limited range (in % of tidal volume). FL was found in 48 % children of R group. No patient of the NR group elicited FL (P<0.001 R vs. NR). The frequency of upper airway collapses was higher in R group (12 children) than in NR gr oup (5 children). In conclusion, a high frequency of tidal FL in the R group was found, while it was not present in NR group. A relatively high frequency of expiratory upper airway collapses was found in both groups, but it did not differ significantly. NEP method represents a reasonable approach for tidal flow limitation testing in non-sedated preschool children., A. Jiřičková, J. Šulc, P. Pohunek, O. Kittnar, A. Dohnalová, J Kofránek., and Obsahuje bibliografii