An in vitro study of a possible correlation between penetration of dentinal tubules by four root canal sealers and microleakage of external fluids into the canal was done using a dye leakage method and scanning electron microscopy, The root canals of 45 teeth were instrumented and the smear layer removed prior to obturation of root canals with gutta-percha and one of four sealers: Diaket, Endomethasone, CRCS or Ketac-Endo, The extent of leakage was scored after immersion in India ink for 72 h. The same specimens were also used for scanning electron microscopic evaluation, There was a statistical difference in leakage patterns between the groups (P < 0.05), Diaket had lower microleakage scores than the other sealers (P < 0.05), When the scores for penetration of sealers into the tubules were analysed, Ketac-Endo demonstrated the least penetration (P < 0.01), There appeared to be a converse relation between tubular penetration and dye leakage, but the correlation was not statistically significant (P > 0.05).