Although reverse transcriptase polymerase chain reaction (RT-PCR) is an extremely sensitive method of mRNA analysis, obtaining quantitative information with this technique can be difficult. This is caused primarily by the fact that there are two sequential enzymatic steps involved: the synthesis of DNA from the RNA template and PCR. In practice, the exponential nature of PCR and the practical aspects of performing PCR pose the most serious obstacles to obtaining quantitative information. With some adaptations, however, RT-PCR can yield accurate quantitative results.