Procedure for the measurement of at least one flow parameter, particularly a flow velocity, a mass flow or a volume flow, of a medium flowing through a pipe, said medium being at least temporarily two-phase or multi-phase of which at least one medium phase is fluid, wherein said procedure comprises the following steps: - The medium to be measured is allowed to flow through at least one measuring tube, particularly vibrating at least temporarily, of an in-line measuring device for flowing media, said measuring tube being inserted in the course of the pipe, - Generation of at least one measuring signal influenced by at least a physical parameter, particularly a density and/or a viscosity, of the medium in the measuring tube using a sensor arrangement of the in-line measuring device which is arranged on the measuring tube and/or in the vicinity of said tube, and reacts at least indirectly to changes of the at least one physical parameter of the medium, - Measurement of pressures, particularly static pressures, acting in the medium, for the repeated determination of a pressure difference which is present in the flowing medium, particularly at least partially along the at least one measuring tube, - Generation of measured values of the first type, which represent in a time sequence, particularly digitally, the at least one medium flow parameter to be measured, taking into account a pressure difference currently determined for the flowing medium, and using a transmission function, which at least determines how the measured values of the first type are generated using the pressure difference currently determined for the flowing medium, - Generation of measured values of the second type, which represent, in a time sequence, the at least one parameter of the medium in the measuring tube or a measured variable of the medium derived from said parameter, using the at least one measuring signal generated using the in-line measuring device, as well as - Repeated monitoring of the flowing medium, particularly using the at least one measuring signal generated using the in-line measuring device to determine whether the medium is at least two-phase, - wherein a measured value of the first type is output as a measured value currently representing the flow parameter to be measured if the medium is detected to be at least two-phase, - wherein the measured values of the second type represent a parameter of the medium which essentially corresponds to the flow parameter represented by the measured values of the first type, and are at least temporarily generated if the medium is essentially single-phase or is at least presumed to be single-phase, and - wherein the transmission function is repeatedly adapted to the medium to be measured taking into account the at least one measuring signal generated using the sensor arrangement of the in-line measuring device, particularly taking into account at least a measured value of the second type. - The medium to be measured is allowed to flow through at least one measuring tube, particularly vibrating at least temporarily, of an in-line measuring device for flowing media, said measuring tube being inserted in the course of the pipe, - Generation of at least one measuring signal influenced by at least a physical parameter, particularly a density and/or a viscosity, of the medium in the measuring tube using a sensor arrangement of the in-line measuring device which is arranged on the measuring tube and/or in the vicinity of said tube, and reacts at least indirectly to changes of the at least one physical parameter of the medium, - Measurement of pressures, particularly static pressures, acting in the medium, for the repeated determination of a pressure difference which is present in the flowing medium, particularly at least partially along the at least one measuring tube, - Generation of measured values of the first type, which represent in a time sequence, particularly digitally, the at least one medium flow parameter to be measured, taking into account a pressure difference currently determined for the flowing medium, and using a transmission function, which at least determines how the measured values of the first type are generated using the pressure difference currently determined for the flowing medium, - Generation of measured values of the second type, which represent, in a time sequence, the at least one parameter of the medium in the measuring tube or a measured variable of the medium derived from said parameter, using the at least one measuring signal generated using the in-line measuring device, as well as - Repeated monitoring of the flowing medium, particularly using the at least one measuring signal generated using the in-line measuring device to determine whether the medium is at least two-phase, - wherein a measured value of the first type is output as a measured value currently representing the flow parameter to be measured if the medium is detected to be at least two-phase, - wherein the measured values of the second type represent a parameter of the medium which essentially corresponds to the flow parameter represented by the measured values of the first type, and are at least temporarily generated if the medium is essentially single-phase or is at least presumed to be single-phase, and - wherein the transmission function is repeatedly adapted to the medium to be measured taking into account the at least one measuring signal generated using the sensor arrangement of the in-line measuring device, particularly taking into account at least a measured value of the second type.