Harm reduction approaches are effective, patient-driven alternatives to abstinence-based treatment for people who are not ready, willing, or able to stop using substances. This volume outlines the scientific basis and historical development of these approaches, and reviews why abstinence-based approaches often do not work. The authors then share their expertise about harm reduction treatment (HaRT), an empirically based approach co-developed with community members impacted by substance-related harm - a first of its kind. The reader learns in detail about the pragmatic mindset and compassionate heartset of HaRT and the three treatment components: measurement and tracking of patient-preferred substance-related metrics, harm-reduction goal setting and achievement, and discussion of safer-use strategies. This volume walks practitioners through all components, provides example scripts for use in daily practice, and illustrates the work through case studies and input from community members. Handouts are available for use in daily practice. This is essential reading for clinical psychologists, psychotherapists, and researchers who encounter people who have substance-use problems.