SummaryAn 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<