Over the last several years, beginning with the California shelf experiment STRESS, a suite of instruments have been developed to measure all 3 properties, namely, suspended size distribution, settling velocity distribution, and the reference concentration [Agrawal & Pottsmith, Marine Geol., 2000]. These systems are all based on measuring multiple-angle scattering of laser light. The measurements are made in the small forward angle region (e.g. 0.1-20 degrees), where scattering is dominated by light diffracted by particles. For diffraction, particle composition is not significant, so that the method is generally applicable to all types of particles. These LISST series instruments have now been used extensively. In this paper, we shall describe the principles, methods, and data from an arry of field experiments. Limitations of the method will also be discussed.