"SHIRASU" is a volcanic deposit and is distributed widely in South Kyushu. The natural deposits on plains of cities such as Kagoshima are transported by running water, therefore composed of the components of the "SHIRASU", and are called a alluvial "SHIRASU" soil, According to our experience, the piles in the alluvial "SHIRASU" soils show special characteristics in skin friction (shaft resistance). The skin friction of the piles was obtained from the results of the experiments of loading tests on the piles in the alluvial "SHIRASU" soil, and was compared with the results of the calculation by the architectural code for the foundation design. The results show that the skin friction of the piles in the alluvial "SHIRASU" soils is greater than the calculated value by the architectural code. Further, it is shown that the skin friction can be estimated from the N-values of standard penetration test.