Monoclonal antibodies have had a pronounced impact in medicine and biology, with a broad array of approved agents that are used for the diagnosis, treatment and characterization of cancers, immunological disorders, and infectious diseases. Because of their exquisite target specificities, together with their favorable pharmacologic properties, antibodies are destined to have even increased clinical impact, particularly in diseases that are understood at the molecular level. This Keystone Symposia meeting will focus attention on many of the key advances in antibody-based technologies as well as on where the field is heading. Some of the critical topics to be covered include: 1) Antibody structure and function; 2) Engineered antibodies and antibody-like molecules for improved efficacy; 3) Antibody pharmacologic properties and biologic distribution; 4) Antibody-based therapies for cancer and infectious diseases; 5) Targeting costimulatory pathways and immunological checkpoints; 6) Antibodies as carriers of drugs, cytokines, radioisotopes and imaging agents; 7) Antibody mimetics; 8) Clinical advancements and challenges. This meeting has become an established forum that attracts both new investigators and leaders in the field, coming from academia, industry and research institutes around the globe. The goals of the meeting will be to address the critical issues facing the broad field of antibody-based therapeutics, provide an overview of recent advances and bring together interdisciplinary groups for the generation of new ideas and promising areas of investigation.