As more manufactured stormwater treatment devices enter the market, stormwater managers are searching for effective and rapid methods for evaluating device performance. Many agencies require vendors to test full-scale versions of their devices under controlled conditions. The most common parameter used to document performance is suspended solids. Many pollutants attach to the solids and a solids simulant is relatively easy to generate. In addition, solids are comparatively easy and inexpensive to quantify. However, a controversy still exists in the professional community as to whether total suspended solids (TSS) or suspended sediment concentration (SSC) should be measured (several agencies require both but only use one to verify device performance). Second, agencies often specify different simulant mixtures for controlled tests. Third, sampling protocols, in particular sample preparation and filter nominal pore diameter, are not well-defined. Sample location in the flow stream can greatly affect the results, as can the procedure used for sample splitting. This paper focuses on the protocol developed and evaluated by two academic testing organizations during recent evaluations of two devices that were evaluated for solids removal performance. This protocol is repeatable and is not specific to solids testing, but allows for a single sample to be split into size fractions for subsequent particle-size and pollutant-association analysis.