The evolution of chlorine bubbles on technologically important anodes has been studied using in situ microscopy and measurements of electrochemical noise. Images of RTO (ruthenium-titanium oxide) electrode surfaces evolving gas show that the surfaces display heterogeneous bubble detachment kinetics. The measurement of current noise at constant potential, allows different electrocatalysts to be compared in terms of bubble evolution rates. Analysis of noise data in the frequency domain suggests that bubble growth site turnover rates are quite low.