The authors discuss a tentative approach to the choice of criteria indicating the optimal suitability of different solid-phase carriers made of polystyrene for use in the enzyme immunoassay (EIA), viz. the dependence of specificity, sensitivity, reproducibility and reliability of EIA results on the adsorption properties, transparency expressed in percent and transparency variations of the plates under test. The evaluation of the carriers by four parameters is proposed with the use of assay plates manufactured by Nunc A/S (Denmark) for control. To ensure the objective evaluation of the suitability of polystyrene plates for use in EIA, the choice of uniform criteria is necessary.