The relationship between defoliation of major tree species (Norway spruce) and the measured and modelled stress factor (acid deposition) was investigated by using statistical analyses. The deposition levels of sulphur and nitrogen compounds in 1994, 1998 and 2000 have been used as a criterion for defoliation of trees taken from the LANDSAT satellite images from 1994 to 2000 due to acidification of forest soil. Wet deposition was derived from concentration values for SO4 2-, NO3 - and NH4 + in precipitation and from precipitation amounts. Dry deposition of SO2, NOx, NO2, NH3 and aerosol particles (SO4 2-, NO3 - and NH4 +) was derived from concentrations of gaseous components and aerosol in the air, and from their deposition velocities. Acid deposition and defoliation of Norway spruce were evaluated at 20 monitoring sites within the Hrubý Jeseník Mountains (north-east part of the Czech Republic) with the following results: parameters, expressing defoliation of crown showed correlation with deposition levels of sulphur and nitrogen. Defoliation in 1997 and 1998 showed a statistically significant positive relationship with a total deposition of sulphur and total potential acid deposition (P < 0.01) in 1994. Defoliation in 1998 showed a statistically significant positive relationship with total deposition of nitrogen (P < 0.01) in 1994. Total defoliation in 1995 showed statistically significant positive relationship with total deposition of reduced nitrogen (P < 0.01) in 1994