Chromatography on oligo(dT) columns is the preferred method for large-scale purification (>25 µg) of poly(A)+ RNA extracted from mammalian cells. Typically, between 1% and 10% of the RNA applied to the oligo(dT) column is recovered as poly(A)+ RNA. Because the method can be frustratingly slow, it is not recommended for purification of poly(A)+ RNA from multiple samples. For this purpose, batch elution (Selection of Poly(A)+ RNA by Batch Chromatography) is the better choice.