Abstract: For calibrating a network analyzer, calibration measurements are successively performed in any desired order on three different calibration standards connected between the two test ports; the first calibration standard is a two-port circuit all of whose complex scatter parameters are known and which is, for example, implemented by a direct connection of the two test ports; the second calibration standard is an attenuator of random transmission but known reflection; the third calibration standard preferably is a two-port circuit exhibiting random reflection which, however, is equal on both sides and different from the reflection of the second calibration standard.