Miniaturized and parallelized sandwich immunoassays allow the simultaneous analysis of a variety of parameters in a single experiment. Bead-based protein array systems or suspension microarrays are well-established multiplex sandwich immunoassay formats. To study inflammatory diseases, protein arrays can be used to analyze changes in plasma protein levels, such as cytokines, chemokines, soluble receptors, and matrix metalloproteinases. Using the bead-based Luminex system, multiplexed sandwich immunoassays have been developed to analyze the plasma concentrations of soluble receptors: sTNF-RI, sTNF-RII, sIL-2R, sgp130, sFas, sRAGE, sE-selectin, sICAM-1, sVCAM-1, sMIF-1 and sFasL. This newly established 11-plex soluble receptors assay demonstrated acceptable intra-assay and inter-assay precision, appropriate accuracy, and no crossreactivity between analytes. Using this assay, 100 plasma samples derived from 36 critically ill intensive care unit (ICU) patients with trauma or sepsis were analyzed for their soluble receptor plasma concentrations. Results obtained allowed grouping of patients' samples into a trauma and a sepsis group. Four candidate molecules: sFas, sICAM-1, sTNF-RI, and sTNF-RII had higher concentrations in patients with sepsis than in those with trauma, contributing the highest discriminatory values to define the nature of the inflammatory disease originating from pathogen-involved (sepsis) or pathogen-independent inflammation.