Traditionally, biodegradation of pentachlorophenol (PCP) in soil is studied by the disappearance of the substrate. Because of the lack of an efficient method to enumerate PCP-degrading bacteria in environmental samples, little information is known about the dynamics of these bacteria in soil. In this study, the efficiency of a modified most-probable-number/polymerase chain reaction (MPN/PCR) protocol was compared to the traditional MPN/¹⁴C-PCP mineralization assay to quantify the cell density of PCP-degrading Pseudomonas sp. UG30 inoculated in a pristine soil. The 744-bp tetrachlorohydroquinone reductive dechlorination gene (pcpC) of UG30 was targeted for the MPN/PCR detection assay. The MPN/PCR protocol had a detection limit of 4 CFU/g of soil. A good coffelation was established between the MPN/PCR estimation and initial inoculum density ranging from 40 to 2 x 10⁹ CFU/g of soil. However, the MPN/¹⁴C-PCP mineralization protocol underestimated the inoculum density by approximately 100-fold. Survival of UG30 in soil was monitored by the MPN/PCR assay. The cell density of the inoculum decreased from 1.4 x 10⁸ to 6.8 x 10⁶ CFU/g of soil in 10 days at 22°C.