This is one in a series of reports examining the prevalence of Adverse Childhood Experiences (ACEs) in the Welsh adult population and their impact on health and well-being across the life course. The series will include reports on: ■ The prevalence of Adverse Childhood Experiences and their association with health-harming behaviours in the Welsh adult population. ■ The impact of Adverse Childhood Experiences on chronic ill health, use of health and social care services and premature mortality in Welsh adults. ■ The impact of Adverse Childhood Experiences on mental well-being in Welsh adults. Preface Over 2,000 adults aged 18-69 years participated in the ACE Study for Wales, providing anonymous information on their exposure to ACEs before the age of 18 years and their health and lifestyles as adults. The study achieved a compliance rate of 49.1% and the sample was designed to be representative of the general population in Wales. Data were collected in participants’ places of residence using an established questionnaire incorporating the short ACE tool developed by the US Centers for Disease Control and Prevention and based on work by Felitti et al (1998) .