The invention relates to a method and a device for determining and/or monitoring the fill level (F) of a medium in a container or, respectively, to a method and a device for establishing the density (ρ) of a medium in the container. The invention allows a highly accurate determination or monitoring of the fill level (F) or the density of a medium in a container. With reference to the method, the object is solved in that the influence of at least one disturbing parameter on the oscillation frequency of an oscillation-capable unit is established and correspondingly compensated in the determination of the fill level (F) of the medium in the container or, respectively, in the determination of the density (ρ) of the medium in the container.