The autocatalytic cyclohexane oxidation was investigated in a lab-scale bubble column reactor with on-line measurement of bubble sizes. Significant conversion was obtained at temperatures between 420 and 430 K. The main products were found to be cyclohexyl-hydroperoxide, cyclohexanol and cyclohexanone. Rising oxygen concentrations favour the production of cyclohexanone. Temperature mainly affects the induction time. At conversion rates greater than 5 % bubble coalescence was inhibited, affecting bubble size distributions for gas hold-ups above 1 %.