In double-step electrochemiluminescence experiments, the luminescence emission transients contain interesting information on the electrode reactions involved, the coupled mass transport and the homogeneous annihilation reaction. It was found that the start of luminescence emission, following the second potential step, occurs only after a delay of the order of 100 mu s. The effect of Forster-type energy transfer from the electronically excited molecules to the metal electrode is insignificant under the experimental conditions considered. Rather, it is shown that this delay is caused by the IR(u) drop, which is closely related to the time constant R(u)C(DL), where R(u) is the uncompensated electrolyte resistance and C-DL is the double-layer capacitance. ECL transients generated with the digital simulation technique using this information agree with the experimental transients. The rate constant of the homogeneous annihilation reaction is derived from such fits.