This study surveyed microbial biomass and its mineralization activity in five anthropogenic grasslands typically contaminated by persistent organic pollutants (polychlorinated biphenyls -PCBs, polycyclic aromatic hydrocarbons -PAHs, DDT). Toxic equivalent (I-TEQ 2378-TCDD; pg•g -1 ) of PCBs congeners decreased in the following order: site T (8.40) > site P (3.10) > site M (1.1) > site PZ (0.92) > site K (0.05). Site M was the only one with increased level of polychlorinated phenols (23.80 μg•g -1 ). Following parameters of stressed microbial communities were evaluated: microbial biomass carbon (MB-C), respiration rate (RR), potential (glucosestimulated) respiration rate (PR), biomass specific respiration activity (qCO 2 ) and long-term glucose uptake incubation experiments where mineralization kinetics is studied simultaneously with the evaluation of MB-C. Estimates of MB-C provided very suitable basis for the evaluation of mineralization capacity. Although the soils were not fully distinguished only on the basis of short-term estimations of RR and PR values, the ratio RR/PR appeared to reflect relatively low capacity of microflora in heavily polluted soils to utilize sufficient amount of available organic matter naturally present in the sites. Significant decline of MB-C content during laboratory incubations without substrate addition also proved low mineralization capacity of soils PZ, P, and particularly of soil T, while soil K was able to maintain present microbial biomass and relatively high mineralization activity. In all the soils, the addition of glucose significantly increased MB-C content and newly synthesized biomass at the end of incubation could be arranged in the following order: K > M > P > PZ > T. Sufficient mineralization capacity and sustainability of microbial biomass was therefore observed in the site K that was not highly polluted by PCBs and DDT. Microflora in the other soils appeared to be limited in mineralization capacity and in * Corresponding author † Ladislav Dušek, Ph. D., 113 Downloaded by [UZH Hauptbibliothek / Zentralbibliothek Zürich] at 07:33 23 December 2014 114 M. SKODA et ai.conversion efficiency of substrate C to biomass C which appeared to be caused mainly by bacteriostatic effect of PCBs.