Using data from the British Millennium Cohort Study (MCS), an ongoing longitudinal study of a cohort of 18,827 children born in the UK in 2000-2001, we investigate important correlates of mental health issues during childhood. MCS respondents were sampled at birth, at age 9 months, and then when they were 3, 5, 7 and 11 years old. Each sweep contains detailed information on the family’s SES, parenting activities, developmental indicators, parental relationship status, and indicators of parental mental health. The Strengths and Difficulties Questionnaire (SDQ) and the related Rutter scale were used to identify behavioral and emotional problems in children. In this paper, childhood problems are separated into four domains: hyperactivity, emotional symptoms, conduct problems, and peer problems. We focus on two aspects of this relationship at ages 5 and 11-the role of temporary and persistent poverty and the role of temporary and persistent mental health problems of mothers and fathers. At ages 11 and 5, without other controls in the model, persistent and transitory poverty have strong estimated associations with all four domains, with somewhat stronger estimated effects for persistent poverty. After a set of controls are added, we document that both persistent levels of poverty and transitions into poverty are strongly associated with levels of and transitions into childhood mental health problems. Similarly, sustained levels and transitions into mothers’ mental health problems are strongly associated with levels and transitions into children’s mental health problems. This is much less so for fathers.