Drug-related deaths have become a major source of premature mortality. This paper presents an analysis of deaths due to acute adverse drug reactions caused by opiates or cocaine in the city of Barcelona over a 5-year period during which figures were stable. Annual mortality rates due to adverse drug reactions of city residents for the 1989-93 period were estimated to be 15.3 per 100,000 people in the 15-49-year age group. Mortality rates for men (25.0) are consistently higher than mortality rates for women (5.8). Mortality rates by age group show different patterns by gender. Males in the 25-29-year group have the highest mortality rate (62.8), almost doubling the rates for the 20-24 (36.1) and 30-34 (33.3)-year groups. The highest differential in age-specific mortality by gender is seen in the 35-39-year age group, where mortality rates for men (21.5) are eight times higher than for women (2.6 per 100,000). The distribution by place of residence, stratifying data across city neighbourhoods and municipal districts displays wide differences between districts in the mean annual rates, ranking between 77.3 and 8.3 per 100,000, a nine-fold magnitude. Differences are even steeper when we break down data by neighbourhood. Although all areas with high adverse drug reactions mortality are areas of low socio-economic level, a more complex association between deprivation and drug use must exist, as other areas with similarly low socio-economic indicators do not suffer from such high mortality. A cross-tabulation of place of residence and district of death shows that for most adverse drug reaction deaths, death takes place in the district of residence but patterns related to districts who attract drug-related deaths and districts who export them may be observed. These results provide new insights into the epidemiology of substance abuse in Barcelona, where it follows patterns that may be similar to those of other major urban areas in Spain, but also in other Southern European countries.