Manipur, a north-eastern state of India bordering Myanmar, has experienced very rapid transmission of the human immunodeficiency virus (HIV) among its vast drug-injecting population. Seroprevalence among intravenous drug users increased from 0 per cent in September 1989 to 50 per cent within six months. With a minimum injecting population of 15,000 and seropositivity of over 50 per cent, the infection quickly spread to the population at large. One per cent of antenatal mothers tested seropositive by 1991. Forming part of the area of South-East Asia known as the Golden Triangle, and producing opium and its derivatives, Myanmar shares a long international border with four States of the region, and populations with a common language and culture move freely across borders. Two other north-eastern states of India bordering Myanmar have faced a similar epidemic within a short period of time. As a result of serosurveillance for HIV since 1986, the epidemic could be detected at an early stage. The present paper provides an account of the results of ongoing comprehensive studies conducted in the north-eastern states of India on drug-related HIV infection, already a serious problem, but possibly still restricted to that region of the country. The prevalence of intravenous drug users, their HIV serological status, the demographic profile, risk behaviour, the spread of the infection to other groups and the problems of harm minimization are also covered.