DNA contamination of RNA preparations can present significant problems, especially for polymerase chain reaction (PCR)-based applications. No RNA extraction procedure excludes DNA entirely. Cytoplasmic RNA can be contaminated with DNA because of nuclei breakage during preparation. Moreover, TRIzol preparations do not exclude plasmids or other small DNA fragments. This article describes the reliable and effective method of eliminating DNA from RNA preparations via DNase digestion. DNase I specifically digests DNA into small oligonucleotides, leaving RNA intact.