Although prostitution is illegal in China as previously noted, commercial sex workers are readily available to itinerant workers and other travelling subpopulations such as longdistance truck drivers (21) . Again as previously noted, condom usage is not widely practiced among prostitutes, HIV knowledge and preventive measures are not well known; and like their nomadic clients, commercial sex workers themselves are also a very mobile subgroup. China's itinerant workforce does not represent the only mobile vectors however. Newfound economic prosperity and individual freedoms have made international travel possible for many, with almost 100 million people visiting China in 2002 and around 17 million Chinese travelling abroad (21) . These individuals may also provide additional vectors for HIV dissemination and importation.