Electron beam was successfully used for the degradation of 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP) in water. The effects of radiation doses on substrate degradation and dechlorination of solutions with concentrations of 50 mg/L for both chlorophenols were investigated. The effects of initial concentration, pH and absence of oxygen on the degradation were also investigated. The concentrations of 2,4-DCP and PCP remaining in solution after irradiation were measured by high-performance liquid chromatograph (HPLC). The results showed that an increased radiation dose led to increased degradation of the chlorophenols and increased Cl- yields. In all cases, the rate of degradation was found to be higher than the corresponding inorganic chloride yield from the parent compound. Deoxygenation was also found to increase the rate of degradation of the chlorophenols in water while degradation under alkaline condition was lower than at low to neutral pH.