The aim of this study was to determine if there is a significant correlation between the in vivo presence of periapical radiolucency and ex vivo apical dye penetration on the same human teeth. Study design. Eighty-four endodontically filled teeth that were scheduled for extraction were classified into 2 groups according to the presence or absence of a periapical radiolucency and further divided into 2 subgroups according to the quality of the root canal filling. After extraction, the apical filling was evaluated by a dye penetration method. Results. The dye extraction evaluation showed no correlation between apical dye penetration and the presence of a periapical radiolucency (not significant), but a statistically significant correlation with the quality of the root canal filling (P ϭ .03). Conclusion. The results of the dye penetration study were correlated to the quality of the root canal filling but had no predictivevalueforthedevelopmentofperiapicalradiolucency.