Abstract: A method for determining measurement uncertainty of measured values of a network analyzer. For every measured value of a respectively-selected measurement type, the measurement uncertainty is calculated in an internal computer of the network analyzer according to modulus and/or phase and displayed together with the respective measured value. Data required for this computation, which result directly from properties and an operating mode of the network analyzer, are stored in databanks allocated to the internal computer and are therefore directly accessible to the internal computer, and only data from additionally-used measurement resources, which differ from the data already stored in the databanks, are entered externally into the databanks, where they are set off against the originally-stored data and included as new data in the calculation of the measurement uncertainty.