Abstract: An apparatus is proposed for measuring the mass of a flowing medium in an air intake tube, in particular, for measuring the aspirated air mass of internal combustion engines. The apparatus has at least one temperature-dependent resistor disposed in the flow of the medium, whose temperature and/or resistance is regulated in accordance with the mass of the medium; the adjustment variable serves as a measurement standard for the mass of the medium. The temperature-dependent resistor is disposed in a gap extending parallel to the flow of the medium, and a deflecting body bridging that gap is disposed upstream of the gap. In orer to prevent soiling of the temperature-dependent resistor inlet conduits for the flow of medium to the gap are provided downstream of the maximum cross section of the deflecting body and these inlet conduits discharge into the gap at an acute angle.