The release of contaminants into the environment is inevitable. Contaminants are released through manufacture and use of products and as a result of treatment and disposal of wastes. Upon release to the environment, contaminants move and respond to a number of interrelated natural and man made factors. Penta-chloro-phenol (PCP) is one such contaminant that has been released into the environment and is known to have serious long term environmental effects. The objective of this study was to determine the effectiveness of biological processes to remediate soil contaminated with Penta-chloro-phenol (PCP). This thesis reviews mechanisms by which soil is contaminated, processes available to remediate soils, and in particular, process requirements for successful bioremediation. The abilities of bacteria to degrade PCP from soil contaminated with PCP was evaluated. Solid phase and slurry phase experiments were examined for their effect on PCP concentration over a four month period at the Department of Technology. Massey University. The objectives of this study were (1) To determine if aeration and inoculation of soil in-situ could produce significant removal of PCP. (2) Determine the effect of concentration on bioremediation rates. (3) Compare in-situ treatment with bio-slurry treatments. The experiments showed that it is possible to remove up to 95% of PCP from contaminated soil by inoculation with bacteria. Inoculum size and aeration were shown to be critical factors in affecting the rate of degradation. The larger the initial inoculum the greater the rate of degradation. Without aeration the inoculum was unable to significantly degrade PCP. The bio-slurry confirmed that PCP could be removed readily from soil to an aqueous state. In an aqueous state PCP is degraded at a faster rate than when it is incorporated into the soil matrix. The results of this work is to show that soil rehabilitation by way of biodegradation is a feasible and attractive process.