The repellence of the plant-derived bicyclic monoterpenoid isoborneol on subterranean termites was assessed in short-term laboratory bioassays. Depending on concentration, application of isoborneol to different soil types was efficient in creating repellent soil barriers, which were not penetrated by workers of Reticulitermes santonensis De Feytaud or R. flavipes Kollar within 2 wk after adding the substance to the substrate. Isoborneol-treated barriers did not affect termite survival. The bioavailability of the active ingredient decreased with increasing clay content of the soil. Evaporation of isoborneol from treated soil increased with increasing particle size of the substrate and could be reduced by covering the soil surface.