Bearing capacity of Concrete Piles is very important in piles design procedures, especially when these piles are to be constructed in unsaturated soils. The contribution of matric suction in unsaturated soils has a great effect on increasing the bearing capacity of the pile due to the adhesion between the soil and the pile surface, this contribution even increases in clayey soils. The other factor that effect the bearing capacity is the soil-pile interface roughness. Rougher surfaces give additional shear resistance due to the interlocking between the soil particles and the pile surface. This book is aimed to study the effect of the variation of degree of saturation on the bearing capacity of concrete piles that vary in their surface roughness. The variation of depth and its effect on shear resistance is also studied; and mathematical models were proposed for predicting the bearing capacity of the pile in unsaturated soils.