Fenton’s reagent was applied for degradation of selected congeners of PCBs (PCB28, PCB52, PCB101, PCB138) present in aqueous solution at ppb concentrations. The effectiveness of degradation by this chemical process was determined and the toxicity of degradation products was evaluated. The experiments lasted 96 hours under stable pH during the whole process. In 24 h intervals the samples were extracted and analyzed by GC, GC/MS and IC. At the same time the Microtox® test was applied to assess the toxicity of the resulting solution. It has been observed that the concentration of two congeners, namely PCB28 and PCB52, decreased rapidly within the first 24 h of the experiment, whereas the two remaining ones (PCB101, PCB138) were degraded poorly. After 96 hours of the process, apart from other oxygenated products, acetate and fumarate also were determined. Concentration of Cl^- ions was only slightly increased, indicating that the substrates were not mineralized.