The ability to synthesize RNA in the lab is critical to many techniques.Radiolabeled and nonisotopically labeled RNA probes, generated in small scale transcription reactions can be used in blot hybridizations and nuclease protection assays. This article includes information on: Requirements For Transcription, RNA Phage Polymerases, Template Options: Plasmids, PCR Products, Oligonuclotides and cDNA, Sense or Antisense, Conventional Or Large Scale Synthesis, Products for In Vitro Transcription.