In 1994, an cohort study of drug users had continued in Longchuan and Luxi counties, Ruili city. The cohort study for drug users had been established since 1992 and total 522 drug users were investigated. Sixty five sera samples were collected, including 26 HIV negatives intravenous drug users in 1992 and 39 of them in 1993. The result shown that 10 sera samples are positives. Of sixty five samples tested, the rate of HIV infectious for IVDU in Ruili, Longchuan and Luxi were 25.0%, 16.3% and 0.0% respectively. Total of 46 HIV positives samples were found from 105 blood samples among the IVDU who were newly included in the cohort study in 1994. Of these samples, the rates of HIV infection in Ruili, Longchuan and Luxi were 61.8%, 38.5% and 0.0% respectively. The result of KAP investigation from 522 drug users has shown that there is a marked difference of the rate of HIV infections in the nationalities, occupations, education (P < 0.01). The main reason contributing the low rate of HIV infections in Luxi county is that the IVDU mainly are the Han nationality with higher education level, as well as travelling less to Burma.