The purpose of this study was to compare the sealing ability of laterally condensed 0.04 and 0.02 tapered gutta percha master cones at different spreader penetration depths and to determine the degree of adaptation between the gutta percha, sealer and dentine interface by scanning elevtron microscope analysis. Eighty extracted anterior human teeth with single, straight canals were divided to two main groups (A,B) of 40 teeth each. Each main group was divided into two subgroups; 20 teeth each (A1, A2, B1, B2). Subgroup A1 was obturated with 0.02 tapered master cone at spreader penetration depth 2 mm from the working length. Teeth in subgroup A2 was obturated similarly except at spreader penetration depth 3mm. teeth in subgroup B1 was obturated similar to subgroup A1 except for 0.04 tapered gutta percha master cone and teeth in subgroup B2 was obturated similar to subgroup B1 except for 0.04 tapered gutta percha master cone. All the obturated teeth were rendered transparent and the apical microleakage was evaluated by dye penetration technique using India ink except two samples from each subgroup were sectioned transversely and examined under SEM to evaluate adaptability of gutta percha, sealer and dentine interface. The results showed that there was no significant difference between subgroups A1 and B2 which showed very similar mean microleakage 2.074+ 0.301 and 2.024 + 0.342. However, subgroup B1 showed the least mean microleakage 1.587+0.410 and subgroup A2 showed the most mean microleakage and 2.557 + 0.329. Results of SEM of subgroups A1 and A2 showed moderate adaptation with dentinal wall were subgroups B1 and B2 showed excellent adaptation at the interface, from the results of this study it was concluded that the sealing ability and adaptation of 0.04 tapered gutta percha is better than 0.02 tapered gutta percha at spreader penetration depth 2mm away from the working length.