Large-molecule drugs (therapeutic proteins, peptides, various forms of antibodies) are more frequently being seen in drug-development pipelines, the majority of which are measured using immunochemical/ligand-binding techniques. The assays utilized for analysis of large-molecule drugs rely heavily upon the quality of the components (e.g., reference materials, antibodies) that are critical to the performance of the assays. Commercially available research-grade materials and kits offer a convenient and simple solution, but also present some unique challenges. This article will explore some examples of issues encountered while employing commercially available kits and reagents.