The development of instruments that allow real-time monitoring of fluorescence within PCR reaction vessels is a significant advance in clinical bacteriology. The technology is very flexible, and many alternative instruments and fluorescent probe systems are currently available. Real-time PCR assays can be completed very rapidly, because no manipulations are required after amplification. Identification of amplification products by probe detection in real time is highly accurate compared with size analysis on gels. Analysis of the progress of the reaction allows accurate quantification of the target sequence over a very wide dynamic range, provided suitable standards are available. Finally, probe melting analysis can detect sequence variants including single base mutations.