In the spring of 2009, a novel (H1N1) influenza A virus began to spread among humans worldwide. Although the 2009 H1N1 is related genetically to swine influenza viruses, human infection has not been connected to pig exposure. Because the virus is now circulating widely in the human population, swine herds are at increased risk of becoming infected. In order to investigate potential outbreaks of the 2009 pandemic virus in pigs, a quantitative real-time reverse transcriptase-polymerase chain reaction (qRT-PCR) for the detection of the (H1N1) 2009 RNA in clinical specimens was developed. To evaluate the applicability of the test as a diagnostic tool in the screening of field specimens from swine, 64 field isolates of North American swine, 5 equine and 48 avian influenza viruses collected during diagnostic investigations were analyzed retrospectively as well as samples collected during an experimental in vivo infection with two novel H1N1 isolates, A/California/04/2009 (H1N1)v virus and A/Mexico/4108/2009 (H1N1)v. The sensitivity of the qRT-PCR was shown to be higher with respect to standard techniques such as virus isolation and the reproducibility was satisfactory. The present unique and highly sensitive assay is able to detect as little as 1 x 10(1) copies of RNA per microl of template and it represents a rapid and useful approach for the screening and quantitation of (H1N1) 2009 RNA in porcine specimens.