Studies of and experiences with the reduction of errors in test sieving are presented. The preparation of the test material and, above all, the errors in sample splitting are included in the considerations. Errors due to the manufacture of test sieves are discussed, for example the influence of the aperture width distribution. The method applied at the Forschungsinstitut für Aufbereitung (FIA) for the inspection and calibration of test sieves is described in detail. The use of test materials for the calibration of sieves is recommended.