Within the past 3 years, North American has seen a marked increase in porcine circovirus type 2 (PCV2) associated disease (PCVAD). The rapid spread of PCVAD has raised important questions about transmission of PCV2. To date, transmission of PCV2 is not well understood; however, PCV2 DNA has been detected in multiple body tissues and most body fluids of the pig. It is generally believed that the main route of transmission is the fecal-oral route. However, due to the rapid spread of PCVAD and the extensive use of artificial insemination in the swine industry, semen transmission has been suggested as a potentially important route of dissemination of PCV2. If that is found to be the case, testing and control measures could be initiated to minimize the risk of spread in semen. It is essential that the industry has a highly sensitive and specific test to detect PCV2 in biological samples such as semen. Through this project we were successful in developing a polymerase chain reaction (PCR) test to detect PCV2 in semen, blood and serum. This is a new, highly sensitive and quantitative test with built-in internal controls for quality assurance. This procedure has now been published and is being adapted for use in several private and university diagnostic laboratories. Since two main types of PCV2 (PCV2a and PCV2b) are now circulating in North America, it was important to use both types in our boar inoculation studies. Mature boars that were PCV2 naive were experimentally infected with either PCV2a or PCV2b. The boars were sampled (semen, blood swabs, and serum collected) 20 times over a 90 day period. A portion of the boars were euthanized at different time points post infection to determine the distribution and amount of PCV2 in reproductive organs and other tissues. Results indicated that both the PCV2a and PCV2b inoculated boars became subclinically-infected, seroconverted, and shed low quantities of PCV2 DNA in semen as determined by quantitative real-time PCR. PCV2 infection had no affect on semen quality. PCV2 was detected earlier in serum than it was in semen and blood swabs. Shedding of PCV2 peaked at 2-3 weeks post infection and in some boars persisted for the duration of the study. A swine bioassay was used to evaluate if the PCV2 (PCV2a and PCV2b) DNA detected in semen is infectious. PCV2-naïve, 4 week old pigs were intraperitoneally inoculated with semen from the experimentally-infected boars. Serum samples were collected and all pigs inoculated intraperitoneally with PCV2 PCR positive semen became viremic and developed anti-PCV2 antibodies. This indicates that PCV2 virus in semen is infectious and breeding or insemination with semen is a potential route of PCV2 transmission. Finally, to evaluate if extended semen is a potential point source of infection, PCV2 positive semen was used to artificially inseminate PCV2-naive gilts. Gilts used for this portion of the study became pregnant and carried the pregnancy until termination of the study at 105 days of gestation. None of the gilts had evidence of PCV2-associated reproductive failure. Weekly blood samples from the inseminated gilts were negative for anti-PCV2 antibodies and serum samples from all fetuses were negative for PCV2 antibodies or virus. In summary, a new, highly sensitive and quantitative PCR for detection of both PCV2a and PCV2b in semen and blood and serum was developed and is now available. PCV2a and PCV2b are shed in low amounts in semen of experimentally-inoculated boars. The PCV2 present in semen is infectious in a swine bioassay model; however, under the conditions of this study we were not able to transmit PCV2 or induce PCV2-associated reproductive failure by artificial insemination using PCV2-positive semen. The current state of knowledge does not support routine testing of semen from AI centers for PCV2 as we do for PRRSV.