PURPOSE: To provide a forum for a diverse audience of investigators, health care providers, patients and policy makers to exchange information on measuring adherence to multiple medications (A2MM). Methods currently employed in the literature to determine adherence to more than one medication at a time, as well as participants’ own experiences with measuring A2MM will be discussed and will contribute to the process of formulating and providing guidance on A2MM measurement methodologies.  DESCRIPTION: Medication adherence is a major issue affecting not only the health of the individual, but also health care systems. Non-adherence is associated with worsening clinical symptoms, increased health care utilization and cost, and poorer health-related quality of life. Most research focuses on measuring adherence to a single medication treating a single disease. However, patients are increasingly prescribed multiple medications to treat a single disease and are often being treated for more than one disease at a time making research into how multi-medication treatment regimens impact adherence both within a disease state and across diseases. With the literature on A2MM being scarce, available methods being inconsistently applied and most methods being poorly described, there is a need for guiding research into measuring A2MM.  This workshop will present the evidence from a systematic literature review on methods for measuring A2MM.