This guideline makes recommendations for the use of psychosocial interventions in the treatment of people who misuse opioids, stimulants and cannabis in the healthcare and criminal justice systems. The patterns of use vary for these drugs, with cannabis the most likely to be used in the UK. Cocaine is the next most commonly used drug in the UK, followed by other stimulants such as amphetamine. Opioids, although presenting the most significant health problem, are used less commonly. A large proportion of people who misuse drugs are polydrug users and do not limit their use to one particular drug. This guideline will not deal with recreational drug use, although opportunistic brief interventions for people who misuse drugs but who are not in formal drug treatment are included. The guideline also does not specifically address drug misuse in pregnancy.