This chapter discusses the isolation and characterization of eukaryotic mRNA, where mRNA fraction can then be eluted by lowering the ionic strength. Phenol extraction procedures yield a mixture of all types of RNA including mRNA, although this is a minor component compared to the large amounts of rRNA. Rather than extracting total RNA directly from the cells it is often more convenient to prepare a crude polyribosome fraction by centrifugation and then extract this with phenol or chloroform to give a crude RNA fraction. All reagents and apparatus should be sterilized before use. Collect reticulocytes from a rabbit to give about thirty millilitres of packed cells and lyse with two volumes of distilled water. Re-extract the first phase and the interphase with an equal volume of buffer and keep the aqueous phase and the interphase with an equal volume of buffer and keep the aqueous.