Afterglow (AG), thermoluminescence (TL) and photoluminescence efficiencies in KCl:Eu were investigated in samples annealed at 773K with high Eu-v c dipole concentration, samples aged at 373K with high aggregate concentration and plastically deformed samples enriched with dislocations. AG and TL efficiencies increase significantly for samples with high concentration of aggregates. Plastically deformed samples show a greater efficiency of AG and TL compared to undeformed samples. However, the formation of aggregates during the ageing procedure is strongly reduced in deformed samples. Furthermore, the low temperature peaks in the TL glow curve are absent in deformed and aged samples. We interpret these results as evidence for the participation of dislocations in the AG process and ascribe the relatively high AG efficiency of aggregates to a preferential formation of aggregates along dislocations.