The Adult Psychiatric Morbidity Survey (APMS) is a series of four repeated cross-sectional surveys of adults living in private households in England. The main aim of the survey series is to collect data on poor mental health among adults in order to facilitate the estimation of the prevalence of psychiatric morbidity, allow for examination of trends over time and gauge the level and nature of treatment and service use. The APMS provides key context for understanding mental illness in England and for informing initiatives in this area.