Real-time PCR is the most popular rapid PCR detection method because the productscan be detected in situ while the reaction progresses, making post PCR processing unnec-essary. Real-time PCR methods make use of fluorescence detection with a built-in fluorimeter.Products can be detected in as little as seven minutes when real-time PCR detection iscombined with new PCR technologies that allow more rapid cycling of the reaction. Gene-specific fluorophore-labeled oligonucleotides such as Molecular Beacons, TaqMan® probes,Amplifluor®, and Scorpion® primers are used to measure fluorescence of the specific gene ofinterest as it is being amplified. Nonspecific detection methods can also be used that are basedon a DNA-binding fluorogenic molecule such as SYBR Green, which fluoresces brightly whenbound to double-stranded (ds)DNA. As the product increases in the vessel, so does the fluores-cence. The drawback is that these fluorogenic dyes bind to all dsDNA and thus nonspecificamplification products and primer-dimers may also be detected during amplification—obscuringthe results. Fluorescently labeled oligonucleotide probes and primers allow more specificdetection of products. There are a number of variations of the fluorescent oligonucleotidedetection techniques; for a review, see Mackay, Arden and Nitsche (2002). Variations of real-time PCR continue to be developed as users become more familiar with this rapid detectiontechnique. One variation uses a combination of both SYBR Green and sequence-specificoligonucleotide probes to acquire several layers of specificity. Real-time PCR is also amenableto multiplexing for more comprehensive identification of one organism or the detection ofmultiple species in one reaction. The main drawbacks of real-time PCR, as compared toconventional PCR, are the high start-up expense for equipment, the high cost of reagents,and the inability to determine the size or total number of amplicons, unless a post analysis ispreformed.