It cannot be disputed that in-house ('home brew') assays have a part to play in the diagnosis of emerging or evolving infections such as avian influenza H5N1. In such circumstances, diagnostic companies can provide Research Use Only (RUO) or analyte specific reagents (ASR) to facilitate development. In contrast, the provision of commercial assays is governed by regulatory approval and subject to regular audit by the relevant regulatory bodies to ensure continued quality process throughout the continuum of product management. From initial design, through to post-launch support, the process has to meet the requirements of the USA Food and Drug Administration (FDA) Quality System Regulation (FDA, 1996) as well as that of the international quality standards, for example ISO 9001 (Int. Standard ISO 9001, 2000). Because of the quality policies that are implemented in the commercial environment, I will argue that, where available, commercial assays should replace in-house methods in order to ensure long term reliability of results.