The reliability of MMEF 25-75/VC in the detection of ventilatory disorders of the small airways has been studied. The test was compared with other which, according to the literature, have displayed great sensitivity in this respect (Vmax 50% and 25%, delta Vmax 50% and 25% and iso-flow volume). The study was performed in 90 individuals and showed a good correlation between the results of MMEF 25-75/VC and the other above-mentioned tests.