The sharpness of the dental explorer will influence the detection rate of dental caries. In order to estimate the variation of point form, the explorers manufactured by four Japanese dental factories were measured with a profile projector. Considerable variation in the sharpness of the explorers were found. Then, to find the difference in caries detection ability between sharp and blunt explorers which were selected from the instruments studied, thirty-seven children of tweleve years of age were examined by the blind recording method performed once with each explorer on each individual. The result showed that the sharp explorer detected more carious lesions than the blunt one at 0.22 DMFT or 0.19 DMFS per child examined. Within the limits of the detection of early lesions, the sharp explorer found 30% more carious cavities than the blunt one. There was a statistically significant difference at a probability less than 0.01. A standardized explorer was suggested and the wear on the point when used for from one to six children was also determined. From this evidence, it becomes clear that point uniformity in dental explorers is essential in epidemiological caries studies. To maintain uniformity, the explorer should be resharpened to a standard point once every three examinaitons.