Methamphetamine (MA), a central nervous system stimulant, has become the leading drug of abuse in Thailand over the past three years. The United Nations' Drug Control Program reported that the most significant increase of illicit drug use worldwide in the1990s was in the consumption of amphetamine-type stimulants (ATS). The WHO estimates more than 35 million regular users of MA worldwide, making it the second most commonly used illicit drug after marijuana. With recent drought and subsequent reduced poppy production in Burma, the Burmese military junta in power has responded to declining foreign reserves by encouraging the production and shipment of massive quantities of methamphetamine into Thailand during the past two years. These mobile factories are very difficult to locate and the MA tablets are easily concealed and smuggled, resulting in easy access and low price in Thailand. There are a range of social and medical consequences of MA abuse: poor performance in schools among students; anxiety; convulsion; brain damage; MA psychosis, characterized by violent behavior, repetitive activity, memory loss and paranoia; and acquiring HIV and other blood-borne infections from administering MA by injection. In Thailand, youth are the leading age group initiating MA use. A recent Thai national survey estimated that 12.4 percent of students between 12 and 20 years used illicit drugs in 1999, of whom 57 percent reportedly have used MA. Thus, there is a compelling public health need to address the issue of MA abuse among adolescents and young adults in northern Thailand. Preventing escalation of drug use practices, particularly with respect to route of drug administration, may prove effective in preventing the spread of HIV among those who have not yet begun injecting; HIV prevalence among injectors in northern Thailand is currently over 30 percent. In response to this public health emergency, we are proposing a randomized, controlled peer-outreach intervention trial targeting methamphetamine users (n=258) and their drug and sexual networks (n=1032) in northern Thailand. We will adapt Latkin's intervention that has been demonstrated effective in the USA in reducing HIV-related risk behaviors among IDUs. The primary study endpoint would be reduction in transition to injection drug use among MA users who currently deny any history of injection. The primary objective of this RCT is to assess the efficacy of a peer educator intervention versus HIV voluntary counseling and testing (VCT) on transition to injection drug use among MA users and their peer networks. The intervention addresses reduction of HIV risk behaviors. A series of behavioral measures for HIV risk, level of MA abuse (including overdose and psychiatric morbidity) and injection use among the index and network members will be used to evaluate the efficacy of the intervention. Secondary objectives include: (1) To compare the incidence of sexually transmitted infections (C trachomatis, N gonorrhea, and, for women, T vaginalis) and Hepatitis C Virus in each study condition; (2) To compare changes in HIV and sexual risk behaviors in each study condition for index participants and network members; and (3) To compare perceived changes in substance use network norms for drug and sexual risk practices in each study condition. This study builds on an active NIDA study (DA11133) of our Thai collaboration, is an appropriate extension of our work on HIV and drug use epidemiology and is responsive to a public health problem of central concern to our host country.