Bioremediation of two diesel-oil-contaminated alpine subsoils, differing in soil type and bedrock, was investigated in laboratory experiments at 10 degrees C after supplementation with an inorganic fertilizer. Initial diesel oil contamination of 4000 mg kg(-1) soil dry matter (dm) was reduced to 380-400 mg kg(-1) dm after 155 days of incubation. In both soils, about 30% of the diesel oil contamination (1200 mg kg(-1) dm) was eliminated by abiotic processes. The residual decontamination (60%-65%) could be attributed to microbial degradation activities. In both soils, the addition of a cold-adapted diesel-oil-degrading inoculum enhanced biodegradation rates only slightly and temporarily. From C/N and N/P ratios (determined by measuring the contents of total hydrocarbons, NH4+ N, NO3- N and PO43- P) of soils it could be deduced that there was no nutrient deficiency during the whole incubation period. Soil biological activities (basal respiration and dehydrogenase activity) corresponded to the course of biodegradation activities in the soils.