Introduction to the special issue on addiction health services: in memory of Douglas Longshore.

This is an Introduction to a special issue in memory of Douglas Longshore, a prominent researcher in the field of addiction health services. The findings from the ten papers in this issue are summarized and discussed within the context of Doug's development as a researcher and the core themes from his work. Three core areas are addressed: (1) internal processes related to change among substance abusers, (2) processes related to ethnicity and gender, and (3) treatment effectiveness, particularly regarding interventions to reduce risk of HIV/AIDS among substance abusers. The implications for addiction health services are discussed with regard to the application of these themes to practice.