This paper presents a new triaxial testing device for unsaturated soils. It describes the main features of the triaxial system including double wall cell, pressure/volume controllers, frictionless volume change device, automatic flushing device, and software. The use of a double wall cell eliminates almost all of the volume change compliance errors inherent to single wall cells while the frictionless volume change device accurately measures the change in sample volume. An important feature presented is the automated flushing device which removes diffused air during unsaturated soil testing. Diffusion causes a small amount of air to escape through high air entry ceramic disks during testing. The diffused air accumulation beneath the ceramic disk affects water flow and volume change measurements. In addition, large air pockets created over time can reduce the contact area between the water and the ceramic, which may eventually cause de-saturation of the ceramic disk. Therefore, diffused air should be regularly eliminated to make accurate water content measurements. The accessories of the new diffused-air flushing device include a computer-controlled ball valve and a water level sensor. The flushing device can be integrated into other unsaturated soil testing systems such as the direct shear apparatus, and soil-water characteristic devices. The software provides sophisticated algorithms for automating all testing procedures including diffused air flushing. Copyright ASCE 2006.