Cooperating with CDC, USA, the Center for AIDS Surveillance, Chinese Academy of Preventive Medicine, first identified the epidemic of HIV-1 C subtype virus in China in 1994. As part of the Eighth-Five National Scientific Program and to get information about the geographical distribution of C subtype of HIV-1 and its epidemic time span in Yunnan, using specific peptide ELISA, we tested 192 anti-HIV-1 positive serums, among intravenous drug users. The results indicated that C subtype of HIV-1 started to appear in Ruili (5.1%) in 1992, and the rates were 12.9% in Ruili and 30.4% in Longchuan in 1993, up to 31.9% in Ruili and 33.3% in Longchuan in 1994. The porpotion of C subtype is increasing among the drug users by year. Whether C subtype would become the main the main epidemic subtype in this areas remains to be under observation.