Objective:To compare the root canal filling density of continuous-wave condensation technique with cold lateral compaction. Methods: Twenty freshly extracted human mandibular premolars with one single canal were selected and divided into two groups,ten teeth each. The root canals were prepared with a rotary system in a crown-down technique and obturated with either cold lateral compaction or continuous-wave condensation with E&Q plus system. All roots were horizontally sectioned at 2,4,6,8 mm from the apical foramen using low-speed saw. The cross-sectional area of the canal and gutta-percha were all measured using an image-analysis program. The percentage of gutta-percha-filled area (PGP) was then calculated. Results: With regard to PGP,no significant difference was found at the levels 2,4,6 mm from apex foramen between two groups,and however PGP of continuous-wave condensation group was significantly higher than that of cold lateral compaction group at 8 mm from apical. Conclusion: The density of continuous-wave condensation technique was superior to lateral compaction technique in middle and coronal portions of canals. However,there was no significant difference in the apical portion of canal between two groups.