The ignition of a stoichiometric ethylene-oxygen mixture diluted with argon was experimentally and computationally studied to gain new insights into the nature of the chemiluminescence that accompanies this process and to obtain some of its quantitative characteristics. The experiments were performed behind reflected shock waves at temperatures of 1270-1820 K and a pressure of similar to 1 bar. The time evolution of the luminescence intensity of the electronically excited C-2*, CH*, and OH* radicals and CO2* molecule was monitored photometrically. The measured temperature dependence of the ignition delay time was found to be in satisfactory agreement with the published data and the results of simulations within the framework of the ChemphysMech_v.1 (Tereza et al., 2010) and AramcoMech_1.3_C-4 (Metcalfe et al., 2013) reaction mechanisms. The possible reaction pathways of formation of C-2*, CH*, OH*, and CO2* were analyzed. It was shown for the first time that, along with the recombination reaction CO + O CO2*, CO2* is formed by the reaction CH + O-2 CO2* + H, which dominates during fuel burnout, whereas the former becomes the main channel of CO2* formation at later stages. The contribution from the reaction C2H + O-2 was demonstrated to play a minor role in the formation of CH* as compared to the C2H + O reaction, at least under the conditions tested.