The effect of soil compaction on dehydrogenase activity of the bulk soil and soil rhizosphere surrounding roots of spring wheat were investigated. The measurements were made at different depths of layered soil profile. The highest dehydrogenase activity was measured in heavily compacted soil, probably as an effect of increased amount of exudates which helps root to growth in compacted soil. The highest difference between dehydrogenase activity in bulk soil and the rhizosphere occurred in the most compacted soil. General decrease of dehydrogenase activity with depth was observed in all objects.