[en] Experimental data on the contaminantion measured within a radius of 30 km from the Paks Nuclear Power Plant due to the accident of the Chernobylsk-4 reactor are given for the period between 28 Apr and 13 Jun 1986. Measurements on airborne and fallout activities, surface contamination of the ground, dose rates of γ radiation, activity concentration of the Danube, of milk, plant and food samples and the activity of human thyroid gland were carried out in the environmental control lab of the Paks NPP. According to the preliminary dose calculations the increment of the radiation exposure of the population is regarded to mount up to the average dose burden for half a year due to natural environmental radiation. (V.N.)