Abstract: An assembly for and method of sampling particle-laden fluids for particulate content and particle size distribution are disclosed herein and utilized at least one cascade impactor adapted to be placed within the fluid stream to be sampled. This impactor includes a number of spaced, successive particle collection stages provided for collecting particles diminishing in size from stage to stage and specifically designed to prevent the rate of low of the fluid stream from any one stage to the next downstream stage from reaching its critical flow rate. The pressure at these stages is individually monitored utilizing individual transducers located in close proximity to the impactor and a monitor remotely located relative to the impactor.