This report is intended to serve as a guide for the selection of appropriate techniques to determine the particle size distribution (PSD) of relatively large dry solid additives for drilling fluids@ especially lost circulation materials (LCMs). Detailed procedures for the utilization of any specific PSD method are not included. The technician should refer to and be guided by the measurement equipment manufacturer??s instructions. The particulates range in size from approximately one micron to as much as several millimeters in diameter@ and are considered ??granular?? in shape@ i.e. relatively isometric (of similar length@ width@ and height). The recommendations in this technical report generally are not applicable to the measurement of the PSD of nonisometric (high aspect ratio) materials such as fibers or flakes.