A method for ascertaining and monitoring the fill level of a medium in a container the method utilizes a fill-level measuring device, wherein, according to the technique of time-domain reflectometry, high-frequency measuring signals are guided via at least one measuring probe in the direction of the medium, reflected on at least one interface of the medium as wanted echo signals or on disturbance locations as disturbance echo signals, and received. A current echo curve is formed from a produced, reference echo signal, wanted echo signals and disturbance echo signals, wherein, at least from a first disturbance echo signal and the reference echo signal, which are caused in a measurement-inactive region of the fill-level measuring device, a base point is located in the current echo curve, and wherein the fill level is ascertained from the distance between the base point and the wanted echo signal formed in a measurement-active region of the fill-level measuring device.