Artificial lattice defects were produced in anthracene and stilbene crystals by irradiation with 14 MeV neutrons; the influence on the pulse shape of fluorescence emission and on the method of “pulse shape discrimination” was investigated. At doses of 200 krad the decay time of the fast scintillation component was shortened about 29 ± 4.5% in anthracene and 9.7 ± 2% in stilbene, independent of the mode of excitation. The time constant of the slow component was increased: in anthracene 12.2 ± 3% for α-excitation and 15.2 ± 3.5% for β-excitation, in stilbene 13 ± 3% ( α) and 56.7 ± 8% ( β). Concerning the method of “pulse shape discrimination”, this change in decay times causes in stilbene only a small decrease and in anthracene an increase in separation between α- and β-particles. All results are in accordance with the present theory of delayed fluorescence. A “medium component” (ca. 50 ns), introduced for a correct fitting of the decay curve, was found to be a part of the delayed fluorescence.