In the last century, the indiscriminate release of organic pollutants into the environment has provoked serious and most often irreversible alterations of natural environmental balance. Indeed, soil contamination by highly toxic compounds has greatly increased with negative, irreversible effects on soil quality and health. Several chemical, biological and biochemical soil properties have been profoundly altered and their main effect has been the continuous lost of soil functions in sustaining the survival of living organisms. Among chemical pollutants recalcitrant compounds like polycyclic aromatic hydrocarbons, phenols and chlorophenols arrive to the soil from different anthropic sources and have high toxicity toward humans, plants and animals. Assessing soil quality is a basic requirement for sustainable land use. When dealing with altered soils, monitoring soil status and its progressive changes gives useful information for a future land utilization. Soil biochemical activities are sensitive to several natural and human-induced changes and may provide an helpful tool to assess soil status, its quality and productivity. For instance enzymes activities represent the mediators of important soil functions and soil biochemical parameters, in general, may be used as early and sensitive indicators of soil ecological stress and restoration. In this work a set of enzymatic activities, covering a large array of soil biochemical processes, and several biochemical parameters, such as basal respiration, microbial biomass C and N as well as the routine physical-chemical properties of a soil artificially contaminated with either phenanthrene (Phe) or pentachlorophenol (PCP), as representative of PAH and chlorophenols were investigated with time. The decrease of both Phe and PCP was monitored as well. The effect of a mixed organic compost added to the soil in two amounts on either Phe and PCP removal and the dynamics of soil properties was also studied. The investigated parameters showed different responses to the applied disturb. Increases, decreases and no variations were observed for most of the measured properties. In general, the application and/or the presence of the polluting substance caused negative effects on the biochemical properties, as assessed by both the enzyme activities and microbial biomass. Soils, however, recovered some of their original properties at least within the investigated incubation time. Attempts were made to find out cause-effect relationships between soils properties, enzyme activities and biochemical properties. Statistical analysis was used to quantify the strength of enzyme activities relationships versus microbiological and chemical properties. Acknowledgment: This research was supported by Ministero dell'Università e della Ricerca, Italy, Programmi di Interesse Nazionale PRIN 2002-2003 and by the INCO-MED Program (Contract ICA3-CT-2002-10033).