A microreactor (50-nL), batch reactors (6-mL), and a flow reactor (11.3-mL) were used to study the oxidation of decachlorobiphenyl (10-CB) in supercritical water. In the microreactor experiments, it was found that complete dissolution of 10-CB occurred at excess O-2 (>93%) and that both hydrolysis and oxidation contributed to 10-CB destruction. In experiments performed with the batch reactors, at excess O-2, 99.2% and 100% 10-CB could be destroyed in SCW without and with Na2CO3, respectively. Addition of the neutralization agent Na2CO3 promoted the destruction rate and reduced reactor corrosion significantly. A reaction mechanism for 10-CB destruction was proposed and this was examined further in flow experiments, where we found that 100% destruction could be achieved.