AbstractChemiluminescent acridinium ester derivatives have been synthesized and covalently attached to suitably modified synthetic DNA oligonucleotides. Attachment of acridinium ester label to primary aliphatic amine group(s) present in the synthetic DNA probe molecule is rapid and efficient. Methods have been developed for efficient separation of acridinium ester‐labelled DNA from unincorporated labelling reagent and underivatized DNA.The basic hydrogen peroxide detection reaction and photon counting conditions for measurement of chemiluminescence emission from acridinium ester‐labelled DNA probes have been optimized. Under optimal conditions, the observed detection limit for the labelled DNA (1:1 mole ratio) is the same as for the free acridinium ester label, which is 2 attomole sensitivity in the best case studied.