It is widely recognized that the level of particulate matter in an injectable product is one measure of quality, directly reflecting the success with which the manufacturer applies good quality control. The current USP XXII 1990 limits for particulate matter derived from knowledge that goes back to the 1970s but does not reflect the quality of the product available today. This presentation will discuss the purpose and background of proposed new limits intended to be adopted in the USP 23 revision cycle. The limits tests are structured in two stages for both Large-Volume and Small-Volume Injections, effectively employing an improved light obscuration method as a screening procedure. Product which fails this stage is then evaluated by a second stage, filtration and microscopic examination using a considerably improved procedure in which all of the container contents are sampled (or pooled to 25 mL) and the filter examined episcopically.