Laser-based techniques for particle-size measurement have become increasingly important in combustion research and many other disciplines. Instruments are continually being developed and improved to meet the demanding geometric, accuracy and other requirements associated with current research and industrial applications. This paper reviews some of the many techniques now used, including those marketed as commercial instruments and those ideas still in the research stage. Two distinct classes of methods are identified : amplitude dependent and amplitude independent. The operating principles of particle-size instrumentation using laser-based techniques, as well as difficulties associated with applying these methods, are discussed. Applications of some techniques in research and industrial situations are also reviewed. The paper provides a comprehensive review for those who are beginning studies in, or starting to apply, any particle-sizing method based on laser illumination.