High-quality starting materials are a prerequisite for any scientific method to be reliable and reproducible, but for the production of monoclonal antibodies (mAbs) for human diagnostics or therapy, and for successful preclinical studies, this is of paramount importance. Standard laboratory chemicals are normally perfectly satisfactory and it should not be necessary for a research laboratory to invest substantial effort in setting up in-house testing procedures. Nevertheless, according to current good manufacturing practice, all raw materials that come into contact with medicinal products need to be controlled and tested for purity and identity. In producing antibodies for clinical trials we find that the best way to do this is to specify pharmacopoeia-grade chemicals whenever possible (these are labeled BP, USP, or EuPh and many are available from Merck, Lutterworth, UK) and to require the supplier to send a certificate of analysis with all raw materials. Any supplier who cannot provide a certificate should be avoided. When goods are delivered, check the labels for conformity with the certificate to check that the tests listed were those actually carried out on the product. Few research laboratories are equipped to carry out formal chemical tests for identity, so we suggest that you critically test the functionality of the final reagent. For example, prepare buffers by mixing calculated weights of components (rather than pH adjustment), then measure the final pH and conductivity to check that they conform to your specification.