[en] Some microorganisms metabolize petroleum compounds. Under favorable environmental conditions, the development of microorganisms can be used to reclamation of contaminated soils. The aim of each bioreclamation technique is to improve these conditions in order to accelerate microorganism activity in the soil. In practice, bioreclamation on an industrial scale is induced through the controlled growth of indigenous microorganisms or through inoculating the soil with specific microorganisms, developed in a lab. These two techniques can be applied either in-situ or ex-situ in the excavated soils. Generally, the growth process includes six phases: the lag phase, the acceleration phase, the exponential phase, the growth decline phase, the stationary phase and the endogenous phase. The goal of each technique is to diminish the time lag, increase the acceleration phase, extend the stationary phase and delay the endogenous phase. However, during the bioreclamation phase, the biochemical processes may postpone the treatment by slowing down its growth,. Very often, the advanced techniques developed in the laboratory does not equate with efficiency on the site itself. On the site, the biomass growth decreases faster then expected because of various interaction processes taking place in contaminated soil. The principal factors described in paper which delay the growth of microorganisms capable of reclaiming petroleum products include the following: competition among microorganisms, unavailability of nutrients, variation of the pH, inadequate moisture, temperature variation, sorption, toxicity of by-products, mutation and impact of additives. The most of the factors are insufficiently recognized, however, impact of some parameters is observed when additives as sawdust and nutrients are added. In similar cases the feasibility studies are necessary before implementation of any technique on industrial scale