Abstract The purpose of this study was to determine the possible correlation between dentin microhardness and dentin tubule density in normal human permanent teeth. A new technique was developed which permitted serial determinations of the micro‐hardness and tubule density of the same group of tubules, beginning near to the dentino‐enamel junction and progressing to the pulp chamber. The results show that there is a highly statistically significant inverse correlation between dentin micro‐hardness and tubular density. Tubular density increased as the pulp chamber was approached. This was associated with a decrease in dentin microhardness, presumably due to a decrease in the amount of intertubular dentin and an increase in individual tubular diameter.