From the standpoint of the durability of the sealants, it is assumed that the sealants should be applied only to the bottom part of the pit and fissure to avoid marginal fracture and wear of the materials. Because of this, a minimum area for the sealant to be applied is required for a stable prevention of dental caries. The purpose of this study was to investigate the effect of viscosity of the sealants and various applicators in the techniques for minimum-area-sealing. Three sealants with various degrees of viscosity were applied to the stone models of a lower first molar by means of four types of applicators. Three operators conducting the experiment were a dentist with two years of experience, a dentist with one year of experience and a student. The time required for administration and the area of sealed pits and fissures were evaluated. The following results were obtained. 1. The sealants with a lower degree of viscosity revealed a shorter administration time and a narrower sealed area. 2. The applicators with thinner nozzles brought about a shorter administration time and a narrower sealed area. 3. The administration time did not exhibit significant differences among the operators, while the sealed area exhibited significant differences. 4. The longer the period of the clinical experience of the operator, the narrower the sealed area obtained. From the above results, it is recommended to select a sealant with low viscosity and utilize an applicator with a thin nozzle or a brush with a fine tip to obtain the minimum-sealing-area. Additionally, prior to the clinical trial, one should become acquainted with the characteristics of the sealant as well as the manipulation of the applicator.