In recent years, the use of particle counting in water treatment plants has increased due largely to the fact that particle counting provides excellent resolution at low turbidity levels. Particle counting is, however, still a young technology and certain issues, including the consistency of counts taken by different instruments and the stability of particle size distributions in samples, still need to be addressed. It would benefit utilities to be able to ship samples to remote laboratories for particle count analysis to ensure uniformity of methodology, sample handling and instrumentation. Of critical importance is the stability of samples when they are shipped. To obtain meaningful information, particle counts after shipping should remain the same as counts taken on site. The AWWA Research Foundation recently sponsored research to address these issues. The research was divided into three phases: evaluation of particle concentration standards; development of a protocol for sample preservation and shipping; and, verification of the sample protocol using samples from a variety of water treatment plants throughout the country. This paper briefly summarizes the first two phases of the research and describes the work completed in the third phase.