Abstract Several acetyl derivatives of luminol were synthesized and their chemiluminescence were studied in water or in DMF-water. The role of the amino group in the chemiluminescence was revealed by comparing the chemiluminescence of luminol (I) with that of N-acetyl-luminol (II). Also, it was found that, in the case of the chemiluminescence of I or II in water, the emitting species did not seem to be the corresponding substituted phthalate ion, while in the case of the chemiluminescence in DMF-water, the 3-aminophthalate or 3-acetylaminophthalate ion could be presumed to be the emitting species.