Laser Techniques are becoming one of the most popular methods of particle size analysis but calibration using existing BCR quartz standards has shown unacceptably high deviations from instrument to instrument. As some of the variations were attributed to the irregular shape and optical properties of the quartz, the BCR decided to develop a new set of spherical reference standards that were to be analysed by the four principle primary sizing methods of Sedimentation, Sieving, Microscopy and the Electrical Sensing Zone (ESZ) method. This paper describes the results of the BCR round-robin exercise using a duplicate set of broad range spherical standards to both develop prescriptive guidelines for each method and to short-list the applicant laboratories for the final analysis of a new set of standards.