This thesis puts opiate use into a historical, geographic and demographic context and then outlines the impact of the emergence of HIV infection on the general population and in particular on injecting drug users. The study described here is longitudinal and community based; a sustained attempt was made to identify all the drug users within one district electoral area and to interview them, first in 1985 and again 1995. There is a high level of mortality and morbidity in this cohort of drug users, which is closely associated with, but not exclusive to, HIV infection. Problem drug use is found in the most marginalised and deprived areas of Dublin City.