Abstract: In order to estimate pollution levels of PCBs and their eco-environmental impacts in the waters of the Pearl River Delta (PRD), a large-scale sampling program was conducted to collect monthly water samples at eight major riverine runoff outlets of the PRD from March 2005 to February 2006, and to measure the concentrations of PCBs. The results showed that the PCB concentrations were 0.19-7.04 ng/L, and that tri-PCBs and tetra-PCBs constituted more than 70% of the total PCB concentration in the samples. Furthermore, about 40% of the samples, mainly those collected between July 2005 and December 2005 at the outlets of the Pearl River Delta, had a total PCB concentration higher than or close to that set in the “Environmental Quality Standards for Surface Water” of China (2 ng/L). Composition analysis and principal component analysis results indicated that the profile of PCBs in the samples collected was similar to that of #1 PCBs produced in China, and those of Aroclor 1242 and Aroclor 1016 produced abroad. This suggests that #1 PCB, Aroclor 1242, and Aroclor 1016 may be the main sources of PCB pollution in the riverine waters of the Pearl River Delta. In addition, PCBs from used imported capacitors, sediment resuspension, atmospheric deposition, and discharge of urban wastewater treatment plants were also important sources of PCBs in the riverine waters.