Since the beginning of the AIDS epidemic, needle exchange programs have been established in several developed countries and have proven effective in reducing AIDS transmission. Very few similar programs, however, have been established in developing countries. Estimates indicate there are about 185,000 drug users in Vietnam, of which roughly 50,000 are intravenous drug users (IDUs). Vietnam has very stringent laws and penalties against drug trafficking, but drug addiction is not considered criminal. HIV was first reported in Vietnam in December 1990; as of December 1996, there were 4,891 reported HIV cases in the country, most of which were among IDUs. A needle exchange program to prevent AIDS among IDUs has been initiated in Hanoi and Ho Chi Minh City as part of comprehensive prevention activities that include using peer outreach workers to reach IDUs, providing IDUs with AIDS prevention information, and distributing clean needles and syringes to IDUs. Program monitoring data indicate outreach workers have been able to reach an increasing number of IDUs and give them new needles and syringes. Nonetheless, the program has encountered certain difficulties: outreach workers are sometimes not allowed to enter shooting galleries; many family members of IDUs have been critical of the program; problems have occurred in contacting IDUs; and IDUs prefer glass over plastic syringes. Further evaluation of the program is required to assess its impact on risk behaviors and AIDS transmission among IDUs. 6 references and 2 tables