The Drug Treatment Outcomes Research Study (DTORS) followed up a baseline sample of drug users from 100 Drug Action Teams (DATs) in England over an initial period of 12 months. The study focused on how drug treatment impacts on outcomes, specifically: levels of drug and alcohol use, offending behaviour, physical and mental health, and wider social outcomes. Furthermore, it examined how, if at all, being referred by the Criminal Justice System affects the outcomes of drug treatment.

The study adopted a longitudinal cohort design comprising of survey interviews with drug users at the outset of treatment, and then 3 and 12 months thereafter.

The study recruited treatment seekers from across 100 randomly selected DATs. The recruitment of treatment seekers took place during a 4 to 5 week sampling window within each DAT area - and all agencies therein. During this period, trained NatCen interviewers were put 'on call' within sampled DAT areas. Those seeking treatment at any agency in the area were asked to meet or speak with an interviewer and invited to participate in the study.