A study was conducted in June 2004 to find out the epidemiology of HIV infection among injecting drug users (IDUs) of Darjeeling District of West Bengal, eastern India. The district headquarter, Darjeeling town, also known as "Queen of Hills," is a beautiful spot situated in Himalayan West Bengal that attracts a large number of tourists each year from all over the world. Another unique feature of the district is that it has international boundaries with three countries, Nepal, Bhutan, and Bangladesh. Siliguri, the part of the district on plains, acts as a transit station for these countries as well as to the entire Himalayan region of West Bengal and neighboring state, Sikkim. It is also a transit point to all northeastern states of India: Assam, Arunachal Pradesh, Nagaland, Manipur, Mizoram, Meghalaya, and Tripura. Two hundred twenty-eight study subjects (IDUs) were included in this community-based cross-sectional study from all four subdivisions of the district. Informed consent was obtained, and then personal interviews, followed by blood testing were performed using unlinked anonymous procedure. The study revealed that overall HIV seroprevalence among IDUs was 11.8% (n = 27; 95% confidence interval, 7.9-16.7), whereas seroprevalence of hepatitis C was found to be 47.7% (n = 97). Prevalence of HIV was higher in subjects from hill districts (13.5%) compared with subjects from the plains (9.2%). It also revealed that most IDUs (75.3%) used "brown sugar," an impure form of heroin, as their major addictive substance followed by injection norphine. Sharing of injecting equipment was found to be as high as 67% among IDUs, and sharing of drugs from common ampules was found to be 35.5% of the studied subjects (n = 93). Most subjects (96%) were found to clean their injecting paraphernalia with plain water. Most IDUs (98%) were found to inject intravenously. About 52% of IDUs visited sex workers one or more times within the last 1 year, and 15% of the interviewed subjects (n = 93) reported to suffer from sexually transmitted diseases during the same period. All the IDUs knew about HIV/AIDS. About 69% of the subjects knew that apparently healthy looking person might have HIV infection. HIV was found to be associated significantly with age of the injectors and duration of injecting practices. The study revealed the epidemic of HIV and hepatitis C among IDU populations at this bordering district of West Bengal for the first time that requires urgent intervention at local, national, and international levels.