The longitudinal course and quality of intimate relationships were tested in relation to maternal depressive symptoms in a sample of 1,275 families from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development. Assessments of mothers' intimate relationship status, intimate relationship quality, and depressive symptoms were obtained on 11 occasions from the birth of a child through age 15. Consistent with predictions, results from hierarchical linear models indicated that maternal depressive symptoms over time were associated with a lower probability of being married and lower levels of relationship quality. The strength of the association between relationship quality and depression was stronger than the linkage between relationship course and depression. Sociodemographic characteristics (e.g., mother age, child gender, ethnicity) were more predictive of trajectories of relationship course than relationship quality. Findings are discussed in terms of efforts to prevent and treat the longitudinal interplay between poor intimate relationship functioning and partners' psychopathology and its implications for the overall health and well-being of parents, couples, and children.