The effect of prior plastic deformation on the precipitation kinetics of europium-doped NaCl, KCl and KBr has been analysed using optical absorption, photoluminescence and electron paramagnetic resonance techniques. In the host NaCl, plastic deformation produces a considerable influence on the Eu precipitation processes into the metastable and stable phases. The introduction of defects by mechanical treatment strongly favours the formation of a second phase precipitate which does not nucleate in the undeformed samples and which can be tentatively identified as either NaEuCl3 or Na2EuCl4. In contrast, in the hosts KCl and KBr, plastic deformation does not influence Eu precipitation into the metastable phase which nucleates at low temperatures (<100 degrees C) and was previously related with the Suzuki phase, indicating that the nucleation of this phase is homogeneous. However, the rate of Eu precipitation into metastable and stable phases with EuX2 structure (X=Cl, Br) which nucleate at high temperatures ( approximately 200 degrees C) is enhanced in the plastically deformed samples, suggesting that the nucleation of these phases is heterogeneous. The effect of dislocation on pre-existing Eu second phase precipitates in both KCl and KBr has also been investigated. The results suggest that moving dislocations cause the re-solution of the preexisting Suzuki precipitates, creating complexes of a much simpler nature, while they create plate-like zones when acting on pre-existing stable dihalide EuX2 second phase precipitates.