When the synthetic estrogen and tumourogenic compound diethylstilbestrol is exposed to horseradish peroxidase (HRP) and H2O2 in the presence of the cationic surfactant hexadecyltrimethylammonium bromide (CTAB), a burst of oxygen consumption and concomitant light emission are observed. The quinone form of the product is not seen in the absorption spectrum because CTAB strongly catalyses its conversion to Z,Z-dienestrol. The emission spectrum shows several peaks. Total emission is dramatically enhanced by chlorophyll and by xanthene dyes. A key intermediate in chemiexcitation is 4-hydroxypropiophenone. The ability to promote chemiexcitation is retained through various generations of metabolites, giving origin to a cascade of excited states. Since the biological effects of diethylstilbestrol appear to be connected with its peroxidative metabolism, chemiexcitation may eventually prove to be of importance in, for example, toxicity of the drug.