In this study, general principles of laser diffraction method and important subjects for the determination of soil particle size distribution by this method are considered, and sampling method, repeatability of results and suitability of tap water in the analysis are investigated. In the laser diffraction analysis 0.1 - 0.5 g sample is adequate. However there is no standard sampling method for taking 0.1 - 0.5 g sample which is representative of the whole sample. In this study a sampling method was proposed and its practicability was discussed. Coefficients of variation of d 10, d 50 and d 90 parameters of samples taken according to proposed method are calculated and compared with upper limit values defined in ISO 13320, and has been shown that suitability of proposed method. Proposed method has advantages also which can be applied simple tools and apparatus without using special devices. In addition to this, effect of water characteristics (air free, purified, tap water and air free tap water) on the laser diffraction analyses results was also investigated. In conclusion, it is found out that there is no drawback in utilizing of tap water in laser diffraction analysis.