The aqueous-phase oxidation of m-xylene and phenol has been studied in a batch autoclave reactor. Both reactions were characterized by an induction period during which little of the organic was oxidized, followed by a rapid reaction phase during which most of the organic was destroyed. The distribution of organic between vapor and liquid and interphase transfer caused by liquid-phase reaction and sampling were considered in the analysis of the data. Over the range of concentrations studied, the length of the induction period is independent of the organic concentration and inversely proportional to the dissolved oxygen concentration. During the rapid reaction phase, the oxidation kinetics are first order in organic and half order in dissolved oxygen. Activation energies for m-xylene and phenol were found to be 103 and 94 kJ/g-mol during the induction period and 89.5 and 112 kJ/g-mol during the rapid reaction phase.