Forty single-rooted human central incisor teeth were biomechanically instrumented. Thirty teeth were divided into three groups of 10 and obturated with laterally condensed gutta-percha and one of three cementing mediums. These were zinc oxide-eugenol root canal cement, cyanoacrylate, and cavity varnish. The remaining 10 teeth were not obturated and served as a control. All of the teeth were suspended in a 1% methylene blue dye for 1 wk. Following sectioning the apical dye penetration was measured, and the leakage values were subjected to statistical analysis. The results showed that the teeth obturated with zinc oxide-eugenol and cyanoacrylate, in conjunction with gutta-percha, exhibited less leakage than the cavity varnish and control groups. This finding was statistically significant (p less than 0.0001). There was, however, no significant difference detected between the zinc oxide-eugenol and cyanoacrylate groups.