This is the first in a series of Evaluation Guides designed to support improvements in practice. Individuals and organisations are increasingly called upon to evaluate the services they provide for drug users. This is a sensible approach because good evaluation has the potential to improve drug services. It can help to identify what works, what needs to be improved and what is ineffective. However, evaluation needs to be useful, practical and realistic.
From the beginning, the process and purpose of the evaluation need to be clearly understood by all parties involved. Evaluation can be a positive learning experience if there is a willingness to look for better ways of designing and delivering interventions. To help improve understanding of these issues this Guide brings together our preferred definitions of commonly used terms and concepts.