A particle-size analyzer was used to determine particle sizes of sediment by an optical technique based on an adjustable circle of light which determines the intermediate axis of the sediment particles shown on a photograph. Data from counting particles in various size ranges can be presented either in the form of a particle count or volumetric analysis. Comparison with standard methods of analysis of particles shows that the particle-size analyzer is well suited for measurements of material larger than 8 millimeters in intermediate diameter.