Publisher Summary This chapter provides five different quality control techniques for RNA preparation: electrophoretic profile of the RNA protocol, ultraviolet spectrophotometry and absorption ratio determination of nucleic acid concentration and purity, sample capacity to support reverse transcriptase polymerase chain reaction (RT-PCR), northern analysis, and sample capacity to support in vitro translation. Every laboratory application involving purified RNA requires an assessment of the quality of the sample. In particular, it is of paramount importance to demonstrate the integrity of the messenger RNA (mRNA) component of the sample. Checking a purified sample of RNA for integrity and overall quality may be accomplished in a variety of ways, some of which are also very good positive-control techniques for a number of downstream applications. Of the methods delineated later, examination of the electrophoretic profile of each sample should always be performed immediately after purification and, if the RNA has been stored for a while, a second aliquot should be tested just prior to use. It should never be assumed that a sample will be handsome because a kit was used for purification or that a sample previously characterized remains intact after storage for several months, even at -80°C.