A prospective multi-agency survey of problem drug use associated with illicit drugs and solvents in the city of Bristol in 1984–1985 found 759 problem drug users, giving a period prevalence rate of 0.4–0.8% of those aged 10–44 years. The group was a young one, with 92% under the age of 35. Over half had problems associated with opiates, mainly illicit heroin; 17% had problems associated with solvents, 9% with cannabis, 13% with stimulants, mainly illicit amphetamine, and 3% with hallucinogens. There was little indication of problematic use of barbiturates or cocaine. The problems associated with drugs and solvents were wide-ranging and not specific for individual drugs. Future community surveys would find it cost-effective to concentrate on the five best sources identified here, and to supplement these with indications of drug-taking among teenagers. The difficulties of using the definition of problem drug use for research and the value of case-register surveys for community drug monitoring are discussed.