The impact of cable insulating oil at various concentrations of non-aqueous phase liquid (NAPL) and over increasing oil-soil contact times on soil microbial respiration and survival of earthworms in soil was studied. The presence of a NAPL increased the mineralization of glucose with a median increase of 32% over a range of oil-soil concentrations and contact times. Oil-contaminated soils showed higher microbial activity, which may possess oil-degrading functions. These oil-contaminated soils were toxic to earthworms although such toxicity decreased with greater soil-oil contact time at lower concentrations.