In this paper the relation between the average lesion depth (1) of artificial carious lesions and the length of microhardness indentations (D) on the surface (the load perpendicular to the surface) is investigated. The results show that an empirical linear relationship does exist between 1 and D for both human and bovine enamel. Linearity has been found for decalcification periods 2–8 days and pH values 4.5 and 4.0. The slope of the curves as well as the load dependency is discussed. The error in the lesion depth determinations is 10–15%. The study also gives a numerical comparison between the average lesion depth in human and in bovine enamel decalcified under the same conditions. After 4 days at pH 4.5 or 4.0, the relations are 1 (bovine) ≈ 1.4 # 1(human) and 1 (bovine) ≈ 1 (human), respectively. The advantage of the technique presented here is that is does not destroy the specimen and is suitable for experiments in in vivo sit